diff --git a/include/sirit/sirit.h b/include/sirit/sirit.h
index 2fe9a1b..69ba27d 100644
--- a/include/sirit/sirit.h
+++ b/include/sirit/sirit.h
@@ -204,6 +204,12 @@ class Module {
     Ref Variable(Ref result_type, spv::StorageClass storage_class,
                  Ref initializer = nullptr);
 
+    // Annotation
+
+    /// Add a decoration to target.
+    Ref Decorate(Ref target, spv::Decoration decoration,
+                 const std::vector<Operand*>& literals = {});
+
     // Literals
     static Operand* Literal(std::uint32_t value);
     static Operand* Literal(std::uint64_t value);
@@ -219,6 +225,8 @@ class Module {
 
     Ref AddDeclaration(Op* op);
 
+    Ref AddAnnotation(Op* op);
+
     std::uint32_t bound{1};
 
     std::set<spv::Capability> capabilities;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index dd2df1d..0adf917 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,8 +1,8 @@
 add_library(sirit
     ../include/sirit/sirit.h
     sirit.cpp
-	op.cpp
-	op.h
+    op.cpp
+    op.h
     stream.cpp
     stream.h
     operand.cpp
@@ -12,7 +12,7 @@ add_library(sirit
     lnumber.h
     lstring.cpp
     lstring.h
-	common_types.h
+    common_types.h
     insts.h
     insts/type.cpp
     insts/constant.cpp
@@ -20,6 +20,7 @@ add_library(sirit
     insts/flow.cpp
     insts/debug.cpp
     insts/memory.cpp
+    insts/annotation.cpp
 )
 target_include_directories(sirit
                            PUBLIC ../include
diff --git a/src/insts/annotation.cpp b/src/insts/annotation.cpp
new file mode 100644
index 0000000..81c9c9b
--- /dev/null
+++ b/src/insts/annotation.cpp
@@ -0,0 +1,21 @@
+/* This file is part of the sirit project.
+ * Copyright (c) 2018 ReinUsesLisp
+ * This software may be used and distributed according to the terms of the GNU
+ * Lesser General Public License version 2.1 or any later version.
+ */
+
+#include "insts.h"
+#include "sirit/sirit.h"
+
+namespace Sirit {
+
+Ref Module::Decorate(Ref target, spv::Decoration decoration,
+                     const std::vector<Operand*>& literals) {
+    auto const op{new Op(spv::Op::OpDecorate)};
+    op->Add(target);
+    AddEnum(op, decoration);
+    op->Add(literals);
+    return AddAnnotation(op);
+}
+
+} // namespace Sirit
diff --git a/src/op.cpp b/src/op.cpp
index 41929bf..f5eec52 100644
--- a/src/op.cpp
+++ b/src/op.cpp
@@ -77,6 +77,12 @@ void Op::Add(const std::vector<Ref>& ids) {
     }
 }
 
+void Op::Add(const std::vector<Operand*>& operands) {
+    for (Operand* operand : operands) {
+        Add(operand);
+    }
+}
+
 u16 Op::WordCount() const {
     u16 count{1};
     if (result_type) {
diff --git a/src/op.h b/src/op.h
index 2a2294d..d0ef39a 100644
--- a/src/op.h
+++ b/src/op.h
@@ -37,6 +37,8 @@ class Op : public Operand {
 
     void Add(const std::vector<Ref>& ids);
 
+    void Add(const std::vector<Operand*>& operands);
+
   private:
     u16 WordCount() const;
 
diff --git a/src/sirit.cpp b/src/sirit.cpp
index 46a7ac7..816615a 100644
--- a/src/sirit.cpp
+++ b/src/sirit.cpp
@@ -55,7 +55,7 @@ std::vector<u8> Module::Assemble() const {
     WriteSet(stream, entry_points);
     // TODO write execution mode
     WriteSet(stream, debug);
-    // TODO write annotations
+    WriteSet(stream, annotations);
     WriteSet(stream, declarations);
     WriteSet(stream, global_variables);
     WriteSet(stream, code);
@@ -99,6 +99,7 @@ Ref Module::AddGlobalVariable(Ref variable) {
 }
 
 Ref Module::AddCode(Op* op) {
+    assert(op);
     code_store.push_back(std::unique_ptr<Op>(op));
     return op;
 }
@@ -121,4 +122,10 @@ Ref Module::AddDeclaration(Op* op) {
     }
 }
 
+Ref Module::AddAnnotation(Op* op) {
+    assert(op);
+    annotations.push_back(std::unique_ptr<Op>(op));
+    return op;
+}
+
 } // namespace Sirit