diff --git a/dust-lang/src/instruction/mod.rs b/dust-lang/src/instruction/mod.rs
index 3f4cc67..0b1d28a 100644
--- a/dust-lang/src/instruction/mod.rs
+++ b/dust-lang/src/instruction/mod.rs
@@ -328,7 +328,7 @@ impl Instruction {
                 let register_type = match left.as_type() {
                     TypeCode::BOOLEAN => TypeCode::BOOLEAN,
                     TypeCode::BYTE => TypeCode::BYTE,
-                    TypeCode::CHARACTER => TypeCode::STRING,
+                    TypeCode::CHARACTER => TypeCode::STRING, // Adding characters concatenates them
                     TypeCode::INTEGER => TypeCode::INTEGER,
                     TypeCode::FLOAT => TypeCode::FLOAT,
                     TypeCode::STRING => TypeCode::STRING,
@@ -339,6 +339,13 @@ impl Instruction {
 
                 Operand::Register(destination, register_type)
             }
+            Operation::SUBTRACT => {
+                let Subtract {
+                    destination, left, ..
+                } = Subtract::from(*self);
+
+                Operand::Register(destination, left.as_type())
+            }
             unsupported => todo!("Support {unsupported}"),
         }
     }
diff --git a/dust-lang/src/vm/action.rs b/dust-lang/src/vm/action.rs
index ddc7d49..51af851 100644
--- a/dust-lang/src/vm/action.rs
+++ b/dust-lang/src/vm/action.rs
@@ -593,7 +593,91 @@ pub fn add(instruction: InstructionFields, thread: &mut Thread) {
     }
 }
 
-pub fn subtract(instruction: InstructionFields, thread: &mut Thread) {}
+pub fn subtract(instruction: InstructionFields, thread: &mut Thread) {
+    let destination = instruction.a_field as usize;
+    let left = instruction.b_field as usize;
+    let left_type = instruction.b_type;
+    let left_is_constant = instruction.b_is_constant;
+    let right = instruction.c_field as usize;
+    let right_type = instruction.c_type;
+    let right_is_constant = instruction.c_is_constant;
+
+    match (left_type, right_type) {
+        (TypeCode::INTEGER, TypeCode::INTEGER) => {
+            let left_value = if left_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(left).as_integer().unwrap()
+                } else {
+                    unsafe { thread.get_constant(left).as_integer().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_integer_register(left)
+            };
+            let right_value = if right_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(right).as_integer().unwrap()
+                } else {
+                    unsafe { thread.get_constant(right).as_integer().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_integer_register(right)
+            };
+            let result = left_value.saturating_sub(*right_value);
+            let register = Register::Value(result);
+
+            thread.set_integer_register(destination, register);
+        }
+        (TypeCode::BYTE, TypeCode::BYTE) => {
+            let left_value = if left_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(left).as_byte().unwrap()
+                } else {
+                    unsafe { thread.get_constant(left).as_byte().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_byte_register(left)
+            };
+            let right_value = if right_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(right).as_byte().unwrap()
+                } else {
+                    unsafe { thread.get_constant(right).as_byte().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_byte_register(right)
+            };
+            let result = left_value.saturating_sub(*right_value);
+            let register = Register::Value(result);
+
+            thread.set_byte_register(destination, register);
+        }
+        (TypeCode::FLOAT, TypeCode::FLOAT) => {
+            let left_value = if left_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(left).as_float().unwrap()
+                } else {
+                    unsafe { thread.get_constant(left).as_float().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_float_register(left)
+            };
+            let right_value = if right_is_constant {
+                if cfg!(debug_assertions) {
+                    thread.get_constant(right).as_float().unwrap()
+                } else {
+                    unsafe { thread.get_constant(right).as_float().unwrap_unchecked() }
+                }
+            } else {
+                thread.get_float_register(right)
+            };
+            let result = left_value - right_value;
+            let register = Register::Value(result);
+
+            thread.set_float_register(destination, register);
+        }
+        _ => unimplemented!(),
+    }
+}
 
 pub fn multiply(instruction: InstructionFields, thread: &mut Thread) {
     let destination = instruction.a_field as usize;
diff --git a/dust-lang/tests/math/subtract.rs b/dust-lang/tests/math/subtract.rs
index e69de29..29877a7 100644
--- a/dust-lang/tests/math/subtract.rs
+++ b/dust-lang/tests/math/subtract.rs
@@ -0,0 +1,167 @@
+use dust_lang::{
+    Chunk, ConcreteValue, FunctionType, Instruction, Operand, Span, Type, Value, compile,
+    instruction::TypeCode, run,
+};
+
+#[test]
+fn subtract_bytes() {
+    let source = "0x28 - 0x02";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Byte),
+        instructions: vec![
+            Instruction::load_encoded(0, 40, TypeCode::BYTE, false),
+            Instruction::load_encoded(1, 2, TypeCode::BYTE, false),
+            Instruction::subtract(
+                2,
+                Operand::Register(0, TypeCode::BYTE),
+                Operand::Register(1, TypeCode::BYTE),
+            ),
+            Instruction::r#return(true, 2, TypeCode::BYTE),
+        ],
+        positions: vec![Span(0, 4), Span(7, 11), Span(0, 11), Span(11, 11)],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::byte(0x26));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}
+
+#[test]
+fn subtract_many_bytes() {
+    let source = "0x28 - 0x02 - 0x02";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Byte),
+        instructions: vec![
+            Instruction::load_encoded(0, 40, TypeCode::BYTE, false),
+            Instruction::load_encoded(1, 2, TypeCode::BYTE, false),
+            Instruction::subtract(
+                2,
+                Operand::Register(0, TypeCode::BYTE),
+                Operand::Register(1, TypeCode::BYTE),
+            ),
+            Instruction::load_encoded(3, 2, TypeCode::BYTE, false),
+            Instruction::subtract(
+                4,
+                Operand::Register(2, TypeCode::BYTE),
+                Operand::Register(3, TypeCode::BYTE),
+            ),
+            Instruction::r#return(true, 4, TypeCode::BYTE),
+        ],
+        positions: vec![
+            Span(0, 4),
+            Span(7, 11),
+            Span(0, 11),
+            Span(14, 18),
+            Span(0, 18),
+            Span(18, 18),
+        ],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::byte(0x24));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}
+
+#[test]
+fn add_floats() {
+    let source = "0.5 - 0.25";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Float),
+        instructions: vec![
+            Instruction::subtract(
+                0,
+                Operand::Constant(0, TypeCode::FLOAT),
+                Operand::Constant(1, TypeCode::FLOAT),
+            ),
+            Instruction::r#return(true, 0, TypeCode::FLOAT),
+        ],
+        positions: vec![Span(0, 10), Span(10, 10)],
+        constants: vec![ConcreteValue::Float(0.5), ConcreteValue::Float(0.25)],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::float(0.25));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}
+
+#[test]
+fn add_many_floats() {
+    let source = "0.5 - 0.25 - 0.25";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Float),
+        instructions: vec![
+            Instruction::subtract(
+                0,
+                Operand::Constant(0, TypeCode::FLOAT),
+                Operand::Constant(1, TypeCode::FLOAT),
+            ),
+            Instruction::subtract(
+                1,
+                Operand::Register(0, TypeCode::FLOAT),
+                Operand::Constant(1, TypeCode::FLOAT),
+            ),
+            Instruction::r#return(true, 1, TypeCode::FLOAT),
+        ],
+        positions: vec![Span(0, 10), Span(0, 17), Span(17, 17)],
+        constants: vec![ConcreteValue::Float(0.5), ConcreteValue::Float(0.25)],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::float(0.0));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}
+
+#[test]
+fn subtract_integers() {
+    let source = "10 - 5";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Integer),
+        instructions: vec![
+            Instruction::subtract(
+                0,
+                Operand::Constant(0, TypeCode::INTEGER),
+                Operand::Constant(1, TypeCode::INTEGER),
+            ),
+            Instruction::r#return(true, 0, TypeCode::INTEGER),
+        ],
+        positions: vec![Span(0, 6), Span(6, 6)],
+        constants: vec![ConcreteValue::Integer(10), ConcreteValue::Integer(5)],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::integer(5));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}
+
+#[test]
+fn subtract_many_integers() {
+    let source = "10 - 5 - 5";
+    let chunk = Chunk {
+        r#type: FunctionType::new([], [], Type::Integer),
+        instructions: vec![
+            Instruction::subtract(
+                0,
+                Operand::Constant(0, TypeCode::INTEGER),
+                Operand::Constant(1, TypeCode::INTEGER),
+            ),
+            Instruction::subtract(
+                1,
+                Operand::Register(0, TypeCode::INTEGER),
+                Operand::Constant(1, TypeCode::INTEGER),
+            ),
+            Instruction::r#return(true, 1, TypeCode::INTEGER),
+        ],
+        positions: vec![Span(0, 6), Span(0, 10), Span(10, 10)],
+        constants: vec![ConcreteValue::Integer(10), ConcreteValue::Integer(5)],
+        ..Chunk::default()
+    };
+    let return_value = Some(Value::integer(0));
+
+    assert_eq!(chunk, compile(source).unwrap());
+    assert_eq!(return_value, run(source).unwrap());
+}