diff --git a/README.md b/README.md
index 2b4163a..9670641 100644
--- a/README.md
+++ b/README.md
@@ -41,9 +41,12 @@ The runtime is built as a register machine with a stack and status flags.
 
 ## Registers
 
-- 8 general purpose registers `r0`-`r7`
-- 8 argument registers `arg0`-`arg7`
-- 8 result registers `res0`-`res7`
+- 16 general purpose registers `r0`-`r15`
+- 16 argument registers `arg0`-`arg15`
+- 16 result registers `res0`-`res15`
+- 16 global registers `g0`-`g15`
+
+Global registers are accessible everywhere. Other registers are only valid within an execution frame (in a routine, or the initial scope).
 
 All registers are 64-bit unsigned integers that can be treated as
 signed, if you want to. Overflow is allowed and reported by status flags.
@@ -336,7 +339,9 @@ Jumping to a label is always safer than a manual skip.
 ; Load status flags from a register
 (ldf Rd)
 
-; Define a register alias. The alias is only valid in the current routine or in the root of the program.
+; Define a register alias. 
+; The alias is only valid in the current routine or in the root of the program.
+; However, if the register is a global register, then the alias is valid everywhere.
 (sym SYM REG)
 
 ; Define a constant. These are valid in the whole program.
diff --git a/crsn/src/asm/data/reg.rs b/crsn/src/asm/data/reg.rs
index a43acba..050c1df 100644
--- a/crsn/src/asm/data/reg.rs
+++ b/crsn/src/asm/data/reg.rs
@@ -14,6 +14,17 @@ pub enum Register {
     Res(u8),
     /// General purpose register
     Gen(u8),
+    /// Global register
+    Global(u8),
+}
+
+impl Register {
+    pub fn is_global(self) -> bool {
+        match self {
+            Register::Global(_) => true,
+            _ => false,
+        }
+    }
 }
 
 impl Display for Register {
@@ -22,6 +33,7 @@ impl Display for Register {
             Register::Arg(n) => write!(f, "arg{}", n),
             Register::Res(n) => write!(f, "res{}", n),
             Register::Gen(n) => write!(f, "r{}", n),
+            Register::Global(n) => write!(f, "g{}", n),
         }
     }
 }
@@ -46,6 +58,12 @@ pub fn parse_reg(name: &str, at: &SourcePosition) -> Result<Register, CrsnError>
         }
         let val: u8 = rn.parse().err_pos(at)?;
         Ok(Register::Gen(val))
+    } else if let Some(rn) = name.strip_prefix("g") {
+        if rn.chars().find(|c: &char| !c.is_ascii_digit()).is_some() {
+            return Err(CrsnError::Parse(format!("Bad register: {}", name).into(), at.clone()))?;
+        }
+        let val: u8 = rn.parse().err_pos(at)?;
+        Ok(Register::Global(val))
     } else {
         Err(CrsnError::Parse(format!("Bad reg name: {}", name).into(), at.clone()))?
     }
diff --git a/crsn/src/asm/mod.rs b/crsn/src/asm/mod.rs
index 48d998b..6798920 100644
--- a/crsn/src/asm/mod.rs
+++ b/crsn/src/asm/mod.rs
@@ -39,6 +39,7 @@ pub fn assemble(source: &str, uniq : &CrsnUniq, mut parsers: Vec<Box<dyn CrsnExt
         state: RefCell::new(ParserState {
             reg_aliases: Default::default(),
             reg_alias_stack: vec![],
+            global_reg_aliases: Default::default(),
             constants: Default::default(),
         }),
     };
diff --git a/crsn/src/asm/parse/mod.rs b/crsn/src/asm/parse/mod.rs
index 20c4bf0..0107c02 100644
--- a/crsn/src/asm/parse/mod.rs
+++ b/crsn/src/asm/parse/mod.rs
@@ -30,6 +30,9 @@ pub struct ParserContext<'a> {
 
 #[derive(Default, Debug)]
 pub struct ParserState {
+    /// Register aliases valid globally
+    pub global_reg_aliases: HashMap<RegisterAlias, Register>,
+
     /// Register aliases within the routine
     pub reg_aliases: HashMap<RegisterAlias, Register>,
 
diff --git a/crsn/src/asm/parse/parse_data.rs b/crsn/src/asm/parse/parse_data.rs
index ac2a7f3..dbc3ffe 100644
--- a/crsn/src/asm/parse/parse_data.rs
+++ b/crsn/src/asm/parse/parse_data.rs
@@ -110,12 +110,16 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
                 let pstate = pcx.state.borrow();
                 if let Some(reg) = pstate.reg_aliases.get(reference) {
                     return Ok(DataDisp::RegObject(*reg))
+                } else if let Some(reg) = pstate.global_reg_aliases.get(reference) {
+                    return Ok(DataDisp::RegObject(*reg))
                 }
 
                 let reg = reg::parse_reg(reference, &pos)?;
 
                 if pstate.reg_aliases.values().find(|v| **v == reg).is_some() {
                     Err(CrsnError::Parse(format!("Sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
+                } else if pstate.global_reg_aliases.values().find(|v| **v == reg).is_some() {
+                    Err(CrsnError::Parse(format!("Global sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
                 } else {
                     Ok(DataDisp::RegObject(reg))
                 }
@@ -136,6 +140,8 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
                 /* register aliases */
                 if let Some(val) = pstate.reg_aliases.get(&s) {
                     return Ok(DataDisp::Register(*val));
+                } else if let Some(val) = pstate.global_reg_aliases.get(&s) {
+                    return Ok(DataDisp::Register(*val));
                 }
 
                 /* register */
@@ -144,6 +150,8 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
                 let pstate = pcx.state.borrow();
                 if pstate.reg_aliases.values().find(|v| **v == reg).is_some() {
                     Err(CrsnError::Parse(format!("Sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
+                } else if pstate.global_reg_aliases.values().find(|v| **v == reg).is_some() {
+                    Err(CrsnError::Parse(format!("Global sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
                 } else {
                     Ok(DataDisp::Register(reg))
                 }
diff --git a/crsn/src/builtin/parse.rs b/crsn/src/builtin/parse.rs
index e2dd050..9d04971 100644
--- a/crsn/src/builtin/parse.rs
+++ b/crsn/src/builtin/parse.rs
@@ -55,18 +55,22 @@ pub(crate) fn parse_op<'a>(op_pos: &SourcePosition, keyword: &str, mut args: Tok
             let mut pstate = pcx.state.borrow_mut();
             if pstate.reg_aliases.contains_key(&alias) {
                 return Err(CrsnError::Parse(format!("Register alias \"{}\" already defined!", alias).into(), rpos));
-            }
-
-            if pstate.constants.contains_key(&alias) {
+            } else if pstate.global_reg_aliases.contains_key(&alias) {
+                return Err(CrsnError::Parse(format!("Register alias \"{}\" already defined (global)!", alias).into(), rpos));
+            } else if pstate.constants.contains_key(&alias) {
                 return Err(CrsnError::Parse(format!("Name \"{}\" already used for a constant!", alias).into(), aliaspos));
+            } else if let Some((name, _)) = pstate.reg_aliases.iter().find(|x| x.1 == &register) {
+                return Err(CrsnError::Parse(format!("Register \"{}\" already aliased as \"{}\"!", register, name).into(), rpos));
+            } else if let Some((name, _)) = pstate.global_reg_aliases.iter().find(|x| x.1 == &register) {
+                return Err(CrsnError::Parse(format!("Register \"{}\" already aliased (globally) as \"{}\"!", register, name).into(), rpos));
             }
 
-            if pstate.reg_aliases.iter().find(|x| x.1 == &register).is_some() {
-                return Err(CrsnError::Parse(format!("Register \"{}\" already aliased!", register).into(), rpos));
+            if register.is_global() {
+                pstate.global_reg_aliases.insert(alias, register);
+            } else {
+                pstate.reg_aliases.insert(alias, register);
             }
 
-            pstate.reg_aliases.insert(alias, register);
-
             return Ok(ParseRes::ParsedNone);
         }
 
@@ -75,7 +79,9 @@ pub(crate) fn parse_op<'a>(op_pos: &SourcePosition, keyword: &str, mut args: Tok
 
             let mut pstate = pcx.state.borrow_mut();
             if pstate.reg_aliases.remove(&alias.0).is_none() {
-                return Err(CrsnError::Parse(format!("Register alias \"{}\" not defined!", alias.0).into(), alias.1));
+                if pstate.global_reg_aliases.remove(&alias.0).is_none() {
+                    return Err(CrsnError::Parse(format!("Register alias \"{}\" not defined!", alias.0).into(), alias.1));
+                }
             }
             return Ok(ParseRes::ParsedNone);
         }
@@ -87,10 +93,10 @@ pub(crate) fn parse_op<'a>(op_pos: &SourcePosition, keyword: &str, mut args: Tok
             let mut pstate = pcx.state.borrow_mut();
             if pstate.constants.contains_key(&name) {
                 return Err(CrsnError::Parse(format!("Constant \"{}\" already defined!", name).into(), namepos));
-            }
-
-            if pstate.reg_aliases.contains_key(&name) {
+            } else if pstate.reg_aliases.contains_key(&name) {
                 return Err(CrsnError::Parse(format!("Name \"{}\" already used for a register alias!", name).into(), namepos));
+            } else if pstate.global_reg_aliases.contains_key(&name) {
+                return Err(CrsnError::Parse(format!("Name \"{}\" already used for a global register alias!", name).into(), namepos));
             }
 
             pstate.constants.insert(name, value);
diff --git a/crsn/src/runtime/frame.rs b/crsn/src/runtime/frame.rs
index 950b682..b71e79f 100644
--- a/crsn/src/runtime/frame.rs
+++ b/crsn/src/runtime/frame.rs
@@ -4,7 +4,7 @@ use crate::asm::data::literal::{Addr, Value};
 
 pub(crate) mod status;
 
-pub const REG_COUNT: usize = 8;
+pub const REG_COUNT: usize = 16;
 
 pub type CallStack = Vec<StackFrame>;
 
diff --git a/crsn/src/runtime/run_thread.rs b/crsn/src/runtime/run_thread.rs
index baecf59..f34a946 100644
--- a/crsn/src/runtime/run_thread.rs
+++ b/crsn/src/runtime/run_thread.rs
@@ -9,7 +9,7 @@ pub use state::RunState;
 use crate::asm::data::literal::Addr;
 use crate::module::{EvalRes, CrsnUniq};
 use crate::runtime::fault::Fault;
-use crate::runtime::frame::StackFrame;
+use crate::runtime::frame::{StackFrame, REG_COUNT};
 use crate::runtime::program::Program;
 
 #[derive(Clone, Copy, Eq, PartialEq, Debug, Ord, PartialOrd)]
@@ -48,6 +48,7 @@ impl RunThread {
             thread_info: ti.clone(),
             frame: StackFrame::new(params.pc, params.args),
             call_stack: vec![],
+            global_regs: [0; REG_COUNT],
             ext_data: Default::default(),
         };
 
diff --git a/crsn/src/runtime/run_thread/state.rs b/crsn/src/runtime/run_thread/state.rs
index ca29bfc..53be796 100644
--- a/crsn/src/runtime/run_thread/state.rs
+++ b/crsn/src/runtime/run_thread/state.rs
@@ -17,6 +17,8 @@ pub struct RunState {
     pub frame: StackFrame,
     /// Call stack
     pub call_stack: CallStack,
+    /// General purpose registers that stay valid for the entire run-time of the thread
+    pub global_regs: [Value; REG_COUNT],
     /// Extension data
     pub ext_data: ExtensionDataStore,
 }
@@ -95,6 +97,7 @@ impl RunState {
     /// Read a `Rd` value
     pub fn read(&mut self, rd: impl Into<Rd>) -> Result<Value, Fault> {
         let rd = rd.into();
+        // TODO dedupe
         match rd.0 {
             RdData::Register(Register::Gen(rn)) => {
                 if likely(rn < REG_COUNT as u8) {
@@ -104,6 +107,14 @@ impl RunState {
                     Err(Fault::RegisterNotExist { reg: Register::Gen(rn) })
                 }
             }
+            RdData::Register(Register::Global(rn)) => {
+                if likely(rn < REG_COUNT as u8) {
+                    trace!("Rd {:?} = {}", rd, self.global_regs[rn as usize]);
+                    Ok(self.global_regs[rn as usize])
+                } else {
+                    Err(Fault::RegisterNotExist { reg: Register::Global(rn) })
+                }
+            }
             RdData::Immediate(v) => Ok(v),
             RdData::Register(Register::Arg(rn)) => {
                 if likely(rn < REG_COUNT as u8) {
@@ -167,6 +178,7 @@ impl RunState {
 
         trace!("WR {:?} := {}", wr, val);
 
+        // TODO dedupe
         match wr.0 {
             WrData::Register(Register::Gen(rn)) => {
                 if likely(rn < REG_COUNT as u8) {
@@ -176,6 +188,14 @@ impl RunState {
                     Err(Fault::RegisterNotExist { reg: Register::Gen(rn) })
                 }
             }
+            WrData::Register(Register::Global(rn)) => {
+                if likely(rn < REG_COUNT as u8) {
+                    self.global_regs[rn as usize] = val;
+                    Ok(())
+                } else {
+                    Err(Fault::RegisterNotExist { reg: Register::Global(rn) })
+                }
+            }
             WrData::Register(Register::Arg(rn)) => {
                 if likely(rn < REG_COUNT as u8) {
                     Err(Fault::RegisterNotWritable { reg: Register::Res(rn) })
diff --git a/examples/globals.csn b/examples/globals.csn
new file mode 100644
index 0000000..fb54c19
--- /dev/null
+++ b/examples/globals.csn
@@ -0,0 +1,11 @@
+(
+    (ld g0 15)
+    (call add_cat)
+    (cmp g0 16
+        (ne? (fault)))
+
+    (proc add_cat
+        (add g0 1)
+        (ret)
+    )
+)
diff --git a/examples/globals_sym.csn b/examples/globals_sym.csn
new file mode 100644
index 0000000..efde1d5
--- /dev/null
+++ b/examples/globals_sym.csn
@@ -0,0 +1,12 @@
+(
+    (sym cats g0)
+    (ld cats 15)
+    (call add_cat)
+    (cmp cats 16
+        (ne? (fault)))
+
+    (proc add_cat
+        (add cats 1)
+        (ret)
+    )
+)