diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4e033eb..6d6c2b6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,9 +67,13 @@ elseif(BISON_VERSION VERSION_LESS 3.0)
 endif()
 
 ## 3. External components
+
 find_package(Boost 1.48 REQUIRED regex system filesystem)
 find_package(LLVM REQUIRED CONFIG)
 
+find_library(YAML_LIBRARIES yaml-cpp)
+find_path(YAML_INCLUDE_DIRS yaml.h /usr/include/yaml-cpp/)
+
 add_definitions(
     ${Boost_DEFINITIONS}
     ${LLVM_DEFINITIONS}
@@ -78,6 +82,7 @@ add_definitions(
 include_directories(
     ${Boost_INCLUDE_DIRS}
     ${LLVM_INCLUDE_DIRS}
+    ${YAML_INCLUDE_DIRS}
 )
 
 ## 4. Build
@@ -92,7 +97,8 @@ flex_target(Scanner Monicelli.lpp ${CMAKE_CURRENT_BINARY_DIR}/Lexer.cpp)
 add_flex_bison_dependency(Scanner Parser)
 
 add_executable(mcc
-    main.cpp Nodes.cpp ModuleRegistry.cpp
+    main.cpp Nodes.cpp
+    ModuleRegistry.cpp ModuleLoader.cpp
     ${BISON_Parser_OUTPUTS} ${FLEX_Scanner_OUTPUTS}
     CppEmitter.cpp BitcodeEmitter.cpp
 )
@@ -110,6 +116,7 @@ llvm_map_components_to_libnames(LLVM_LIBRARIES
 target_link_libraries(mcc
     ${Boost_LIBRARIES}
     ${LLVM_LIBRARIES}
+    ${YAML_LIBRARIES}
 )
 
 ## 6. Build the runtime library too
diff --git a/ModuleLoader.cpp b/ModuleLoader.cpp
new file mode 100644
index 0000000..75d157d
--- /dev/null
+++ b/ModuleLoader.cpp
@@ -0,0 +1,55 @@
+#include "Nodes.hpp"
+#include "ModuleRegistry.hpp"
+#include "ModuleLoader.hpp"
+
+#include <yaml-cpp/yaml.h>
+#include <string>
+
+using namespace monicelli;
+
+
+static
+Type toType(std::string const& value) {
+    if (value == "int") {
+        return Type::INT;
+    } else if (value == "float") {
+        return Type::FLOAT;
+    } else if (value == "double") {
+        return Type::DOUBLE;
+    } else if (value == "char") {
+        return Type::CHAR;
+    } else if (value == "bool") {
+        return Type::BOOL;
+    } else {
+        return Type::VOID;
+    }
+}
+
+void monicelli::loadModule(std::string const& from, ModuleRegistry &to) {
+    YAML::Node module  = YAML::LoadFile(from);
+
+    if (!module["functions"]) return;
+
+    for (auto const& proto: module["functions"]) {
+        PointerList<FunArg> *args = new PointerList<FunArg>();
+        for (auto const& arg: proto.second["args"]) {
+            args->push_back(new FunArg(
+                new Id(arg.first.as<std::string>()),
+                toType(arg.second.as<std::string>()),
+                false
+            ));
+        }
+
+        Type type;
+        if (proto.second["type"]) {
+            type = toType(proto.second["type"].as<std::string>());
+        } else {
+            type = Type::VOID;
+        }
+
+        to.registerFunction(new FunctionPrototype(
+            new Id(proto.first.as<std::string>()), type, args
+        ));
+    }
+}
+
diff --git a/ModuleLoader.hpp b/ModuleLoader.hpp
new file mode 100644
index 0000000..74f21da
--- /dev/null
+++ b/ModuleLoader.hpp
@@ -0,0 +1,10 @@
+#ifndef MODULE_LOADER_HPP
+#define MODULE_LOADER_HPP
+
+namespace monicelli {
+
+void loadModule(std::string const& from, monicelli::ModuleRegistry &to);
+
+}
+
+#endif
diff --git a/main.cpp b/main.cpp
index 293a9c3..d5e5e0d 100644
--- a/main.cpp
+++ b/main.cpp
@@ -21,6 +21,7 @@
 #include "Parser.hpp"
 #include "CppEmitter.hpp"
 #include "ModuleRegistry.hpp"
+#include "ModuleLoader.hpp"
 #include "BitcodeEmitter.hpp"
 
 #include <llvm/Bitcode/ReaderWriter.h>
@@ -41,9 +42,27 @@ using namespace monicelli;
 int main(int argc, char **argv) {
     registerStdLib(getModuleRegistry());
 
+    boost::regex namere("^(.+)\\.mc$");
+    boost::regex modulere("^(.+)\\.mm$");
+
+    std::vector<std::string> sources;
+    std::vector<std::string> modules;
+
     for (int i = 1; i < argc; ++i) {
-        std::string inputname(argv[i]);
-        std::ifstream instream(inputname);
+        std::string arg(argv[i]);
+        if (boost::regex_match(arg, namere)) {
+            sources.push_back(arg);
+        } else if (boost::regex_match(arg, modulere)) {
+            modules.push_back(arg);
+        }
+    }
+
+    for (std::string const& name: modules) {
+        loadModule(name, getModuleRegistry());
+    }
+
+    for (std::string const& name: sources) {
+        std::ifstream instream(name);
 
         Program program;
         Scanner scanner(&instream);
@@ -56,8 +75,7 @@ int main(int argc, char **argv) {
 
         parser.parse();
 
-        boost::regex namere("^(.+)\\.mc$");
-        std::string outputname = boost::filesystem::path(inputname).filename().native();
+        std::string outputname = boost::filesystem::path(name).filename().native();
 
         if (boost::regex_match(outputname, namere)) {
             outputname = boost::regex_replace(outputname, namere, "$1.bc");