diff --git a/src/asm/Memory.go b/src/asm/Memory.go
index 903ff15..0af7c38 100644
--- a/src/asm/Memory.go
+++ b/src/asm/Memory.go
@@ -35,9 +35,27 @@ func (mem *Memory) Format(custom string) string {
 		tmp.WriteString(strconv.Itoa(int(mem.Offset)))
 	}
 
-	tmp.WriteString("], ")
-	tmp.WriteString(custom)
+	tmp.WriteString("]")
+
+	if custom != "" {
+		tmp.WriteString(", ")
+		tmp.WriteString(custom)
+	}
+
 	tmp.WriteString(", ")
 	tmp.WriteString(strconv.Itoa(int(mem.Length)))
 	return tmp.String()
 }
+
+// String returns a human readable version.
+func (mem *Memory) String() string {
+	return mem.Format("")
+}
+
+// Memory adds an instruction with a memory address.
+func (a *Assembler) Memory(mnemonic Mnemonic, address Memory) {
+	a.Instructions = append(a.Instructions, Instruction{
+		Mnemonic: mnemonic,
+		Data:     &address,
+	})
+}
diff --git a/src/asmc/call.go b/src/asmc/call.go
index e5d08a7..7a4f51a 100644
--- a/src/asmc/call.go
+++ b/src/asmc/call.go
@@ -32,5 +32,8 @@ func (c *compiler) call(x asm.Instruction) {
 
 	case *asm.Register:
 		c.code = x86.CallRegister(c.code, data.Register)
+
+	case *asm.Memory:
+		c.code = x86.CallAtMemory(c.code, data.Base, data.Offset)
 	}
 }
diff --git a/src/asmc/dllCall.go b/src/asmc/dllCall.go
index 75523d1..71d1e0e 100644
--- a/src/asmc/dllCall.go
+++ b/src/asmc/dllCall.go
@@ -9,7 +9,7 @@ import (
 
 func (c *compiler) dllCall(x asm.Instruction) {
 	size := 4
-	c.code = x86.CallAtAddress(c.code, 0x00_00_00_00)
+	c.code = x86.CallAt(c.code, 0x00_00_00_00)
 	position := len(c.code) - size
 	label := x.Data.(*asm.Label)
 
diff --git a/src/core/CompileCall.go b/src/core/CompileCall.go
index 7e47f48..9d94c2b 100644
--- a/src/core/CompileCall.go
+++ b/src/core/CompileCall.go
@@ -75,10 +75,7 @@ func (f *Function) CompileCall(root *expression.Expression) ([]types.Type, error
 		f.Register(asm.CALL, value.Register)
 
 	case *eval.Memory:
-		tmp := f.NewRegister()
-		f.MemoryRegister(asm.LOAD, value.Memory, tmp)
-		f.Register(asm.CALL, tmp)
-		f.FreeRegister(tmp)
+		f.Memory(asm.CALL, value.Memory)
 	}
 
 	return nil, nil
diff --git a/src/register/Memory.go b/src/register/Memory.go
new file mode 100644
index 0000000..60c62db
--- /dev/null
+++ b/src/register/Memory.go
@@ -0,0 +1,8 @@
+package register
+
+import "git.urbach.dev/cli/q/src/asm"
+
+func (f *Machine) Memory(mnemonic asm.Mnemonic, memory asm.Memory) {
+	f.Assembler.Memory(mnemonic, memory)
+	f.postInstruction()
+}
diff --git a/src/x86/Call.go b/src/x86/Call.go
index b6c9194..a19c68e 100644
--- a/src/x86/Call.go
+++ b/src/x86/Call.go
@@ -34,9 +34,9 @@ func CallRegister(code []byte, register cpu.Register) []byte {
 	)
 }
 
-// CallAtAddress calls a function at the address stored at the given memory address.
+// CallAt calls a function at the address stored at the given memory address.
 // The memory address is relative to the next instruction.
-func CallAtAddress(code []byte, address uint32) []byte {
+func CallAt(code []byte, address uint32) []byte {
 	return append(
 		code,
 		0xFF,
@@ -47,3 +47,33 @@ func CallAtAddress(code []byte, address uint32) []byte {
 		byte(address>>24),
 	)
 }
+
+// CallAtMemory calls a function at the address stored at the given memory address.
+// The memory address is relative to the next instruction.
+func CallAtMemory(code []byte, register cpu.Register, offset int8) []byte {
+	mod := AddressMemory
+
+	if offset != 0 || register == RBP || register == R13 {
+		mod = AddressMemoryOffset8
+	}
+
+	reg := byte(0b010)
+	rm := register
+
+	if rm > 0b111 {
+		code = append(code, 0x41)
+		rm &= 0b111
+	}
+
+	code = append(code, 0xFF, ModRM(mod, reg, byte(rm)))
+
+	if register == RSP || register == R12 {
+		code = append(code, SIB(Scale1, 0b100, 0b100))
+	}
+
+	if mod == AddressMemoryOffset8 {
+		code = append(code, byte(offset))
+	}
+
+	return code
+}
diff --git a/src/x86/Call_test.go b/src/x86/Call_test.go
index 5aae357..033ee64 100644
--- a/src/x86/Call_test.go
+++ b/src/x86/Call_test.go
@@ -37,3 +37,51 @@ func TestCallRegister(t *testing.T) {
 		assert.DeepEqual(t, code, pattern.Code)
 	}
 }
+
+func TestCallAtMemory(t *testing.T) {
+	usagePatterns := []struct {
+		Register cpu.Register
+		Offset   int8
+		Code     []byte
+	}{
+		{x86.RAX, 0, []byte{0xFF, 0x10}},
+		{x86.RCX, 0, []byte{0xFF, 0x11}},
+		{x86.RDX, 0, []byte{0xFF, 0x12}},
+		{x86.RBX, 0, []byte{0xFF, 0x13}},
+		{x86.RSP, 0, []byte{0xFF, 0x14, 0x24}},
+		{x86.RBP, 0, []byte{0xFF, 0x55, 0x00}},
+		{x86.RSI, 0, []byte{0xFF, 0x16}},
+		{x86.RDI, 0, []byte{0xFF, 0x17}},
+		{x86.R8, 0, []byte{0x41, 0xFF, 0x10}},
+		{x86.R9, 0, []byte{0x41, 0xFF, 0x11}},
+		{x86.R10, 0, []byte{0x41, 0xFF, 0x12}},
+		{x86.R11, 0, []byte{0x41, 0xFF, 0x13}},
+		{x86.R12, 0, []byte{0x41, 0xFF, 0x14, 0x24}},
+		{x86.R13, 0, []byte{0x41, 0xFF, 0x55, 0x00}},
+		{x86.R14, 0, []byte{0x41, 0xFF, 0x16}},
+		{x86.R15, 0, []byte{0x41, 0xFF, 0x17}},
+
+		{x86.RAX, 1, []byte{0xFF, 0x50, 0x01}},
+		{x86.RCX, 1, []byte{0xFF, 0x51, 0x01}},
+		{x86.RDX, 1, []byte{0xFF, 0x52, 0x01}},
+		{x86.RBX, 1, []byte{0xFF, 0x53, 0x01}},
+		{x86.RSP, 1, []byte{0xFF, 0x54, 0x24, 0x01}},
+		{x86.RBP, 1, []byte{0xFF, 0x55, 0x01}},
+		{x86.RSI, 1, []byte{0xFF, 0x56, 0x01}},
+		{x86.RDI, 1, []byte{0xFF, 0x57, 0x01}},
+		{x86.R8, 1, []byte{0x41, 0xFF, 0x50, 0x01}},
+		{x86.R9, 1, []byte{0x41, 0xFF, 0x51, 0x01}},
+		{x86.R10, 1, []byte{0x41, 0xFF, 0x52, 0x01}},
+		{x86.R11, 1, []byte{0x41, 0xFF, 0x53, 0x01}},
+		{x86.R12, 1, []byte{0x41, 0xFF, 0x54, 0x24, 0x01}},
+		{x86.R13, 1, []byte{0x41, 0xFF, 0x55, 0x01}},
+		{x86.R14, 1, []byte{0x41, 0xFF, 0x56, 0x01}},
+		{x86.R15, 1, []byte{0x41, 0xFF, 0x57, 0x01}},
+	}
+
+	for _, pattern := range usagePatterns {
+		t.Logf("call [%s+%d]", pattern.Register, pattern.Offset)
+		code := x86.CallAtMemory(nil, pattern.Register, pattern.Offset)
+		assert.DeepEqual(t, code, pattern.Code)
+	}
+}
diff --git a/src/x86/x86_test.go b/src/x86/x86_test.go
index 02e0560..9d6b3bc 100644
--- a/src/x86/x86_test.go
+++ b/src/x86/x86_test.go
@@ -9,7 +9,7 @@ import (
 
 func TestX86(t *testing.T) {
 	assert.DeepEqual(t, x86.Call(nil, 1), []byte{0xE8, 0x01, 0x00, 0x00, 0x00})
-	assert.DeepEqual(t, x86.CallAtAddress(nil, 1), []byte{0xFF, 0x15, 0x01, 0x00, 0x00, 0x00})
+	assert.DeepEqual(t, x86.CallAt(nil, 1), []byte{0xFF, 0x15, 0x01, 0x00, 0x00, 0x00})
 	assert.DeepEqual(t, x86.ExtendRAXToRDX(nil), []byte{0x48, 0x99})
 	assert.DeepEqual(t, x86.MoveRegisterNumber(nil, 0, 1), []byte{0xB8, 0x01, 0x00, 0x00, 0x00})
 	assert.DeepEqual(t, x86.MoveRegisterNumber(nil, 1, 1), []byte{0xB9, 0x01, 0x00, 0x00, 0x00})