diff --git a/workspace_tools/build.py b/workspace_tools/build.py
index 0f9593a3bf..1cf2eb4acb 100644
--- a/workspace_tools/build.py
+++ b/workspace_tools/build.py
@@ -52,6 +52,8 @@ if __name__ == '__main__':
                       default=False, help="Verbose diagnostic output")
     parser.add_option("-b", "--ublox", action="store_true", dest="ublox",
                       default=False, help="Compile the u-blox library")
+    parser.add_option("-D", "", action="append", dest="macros",
+                      help="Add a macro definition")
     (options, args) = parser.parse_args()
     
     # Get target list
@@ -92,10 +94,12 @@ if __name__ == '__main__':
             try:
                 mcu = TARGET_MAP[target]
                 build_mbed_libs(mcu, toolchain, options=options.options,
-                                verbose=options.verbose, clean=options.clean)
+                                verbose=options.verbose, clean=options.clean,
+                                macros=options.macros)
                 for lib_id in libraries:
                     build_lib(lib_id, mcu, toolchain, options=options.options,
-                              verbose=options.verbose, clean=options.clean)
+                              verbose=options.verbose, clean=options.clean,
+                              macros=options.macros)
                 successes.append(id)
             except Exception, e:
                 if options.verbose:
diff --git a/workspace_tools/build_api.py b/workspace_tools/build_api.py
index e965435d17..2c95d92366 100644
--- a/workspace_tools/build_api.py
+++ b/workspace_tools/build_api.py
@@ -26,9 +26,9 @@ from workspace_tools.libraries import Library
 
 def build_project(src_path, build_path, target, toolchain_name,
         libraries_paths=None, options=None, linker_script=None,
-        clean=False, notify=None, verbose=False, name=None):
+        clean=False, notify=None, verbose=False, name=None, macros=None):
     # Toolchain instance
-    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options, notify)
+    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options, notify, macros)
     toolchain.VERBOSE = verbose
     toolchain.build_all = clean
 
@@ -40,7 +40,6 @@ def build_project(src_path, build_path, target, toolchain_name,
     # Scan src_path and libraries_paths for resources
     resources = toolchain.scan_resources(src_paths[0])
     for path in src_paths[1:]:
-        print "PATH:", path
         resources.add(toolchain.scan_resources(path))
     if libraries_paths is not None:
         src_paths.extend(libraries_paths)
@@ -78,7 +77,7 @@ verbose: Write the actual tools command lines if True
 """
 def build_library(src_paths, build_path, target, toolchain_name,
          dependencies_paths=None, options=None, name=None, clean=False,
-         notify=None, verbose=False):
+         notify=None, verbose=False, macros=None):
     if type(src_paths) != ListType: src_paths = [src_paths]
     
     for src_path in src_paths:
@@ -86,7 +85,7 @@ def build_library(src_paths, build_path, target, toolchain_name,
             raise Exception("The library source folder does not exist: %s", src_path)
     
     # Toolchain instance
-    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options, notify)
+    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options, notify, macros)
     toolchain.VERBOSE = verbose
     toolchain.build_all = clean
     
@@ -136,14 +135,14 @@ def build_lib(lib_id, target, toolchain, options=None, verbose=False, clean=Fals
 
 
 # We do have unique legacy conventions about how we build and package the mbed library
-def build_mbed_libs(target, toolchain_name, options=None, verbose=False, clean=False):
+def build_mbed_libs(target, toolchain_name, options=None, verbose=False, clean=False, macros=None):
     # Check toolchain support
     if toolchain_name not in target.supported_toolchains:
         print '\n%s target is not yet supported by toolchain %s' % (target.name, toolchain_name)
         return
     
     # Toolchain
-    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options)
+    toolchain = TOOLCHAIN_CLASSES[toolchain_name](target, options, macros=macros)
     toolchain.VERBOSE = verbose
     toolchain.build_all = clean
     
@@ -192,3 +191,4 @@ def build_mbed_libs(target, toolchain_name, options=None, verbose=False, clean=F
     objects.remove(retargeting)
     toolchain.build_library(objects, BUILD_TOOLCHAIN, "mbed")
     toolchain.copy_files(retargeting, BUILD_TOOLCHAIN)
+
diff --git a/workspace_tools/make.py b/workspace_tools/make.py
index 2abca9a22b..99d5d5272b 100644
--- a/workspace_tools/make.py
+++ b/workspace_tools/make.py
@@ -48,7 +48,9 @@ if __name__ == '__main__':
                       help="The name of the desired test program")
     parser.add_option("-v", "--verbose", action="store_true", dest="verbose",
                       default=False, help="Verbose diagnostic output")
-    
+    parser.add_option("-D", "", action="append", dest="macros",
+                      help="Add a macro definition")
+
     # Local run
     parser.add_option("-d", "--disk", dest="disk",
                       default=None, help="The mbed disk")
@@ -114,7 +116,8 @@ if __name__ == '__main__':
         bin = build_project(test.source_dir, build_dir, target, toolchain,
                             test.dependencies, options.options,
                             linker_script=options.linker_script,
-                            clean=options.clean, verbose=options.verbose)
+                            clean=options.clean, verbose=options.verbose,
+                            macros=options.macros)
         print 'Image: %s' % bin
         
         if options.disk:
diff --git a/workspace_tools/toolchains/__init__.py b/workspace_tools/toolchains/__init__.py
index 29fbf34f15..a5ee60d497 100644
--- a/workspace_tools/toolchains/__init__.py
+++ b/workspace_tools/toolchains/__init__.py
@@ -146,7 +146,7 @@ class mbedToolchain:
     GOANNA_FORMAT = "[Goanna] warning [%FILENAME%:%LINENO%] - [%CHECKNAME%(%SEVERITY%)] %MESSAGE%"
     GOANNA_DIAGNOSTIC_PATTERN = re.compile(r'"\[Goanna\] (?P<severity>warning) \[(?P<file>[^:]+):(?P<line>\d+)\] \- (?P<message>.*)"')
 
-    def __init__(self, target, options=None, notify=None):
+    def __init__(self, target, options=None, notify=None, macros=None):
         self.target = target
         self.name = self.__class__.__name__
         self.hook = hooks.Hook(target, self)
@@ -162,6 +162,7 @@ class mbedToolchain:
             self.options = []
         else:
             self.options = options
+        self.macros = macros or []
         self.options.extend(BUILD_OPTIONS)
         if self.options:
             self.info("Build Options: %s" % (', '.join(self.options)))
@@ -347,7 +348,7 @@ class mbedToolchain:
             self.progress("compile", source, build_update=True)
             
             # Compile
-            command = cc + ['-D%s' % s for s in self.get_symbols()] + ["-I%s" % i for i in includes] + ["-o", object, source]
+            command = cc + ['-D%s' % s for s in self.get_symbols() + self.macros] + ["-I%s" % i for i in includes] + ["-o", object, source]
             if hasattr(self, "get_dep_opt"):
                 command.extend(self.get_dep_opt(dep_path))
             
diff --git a/workspace_tools/toolchains/arm.py b/workspace_tools/toolchains/arm.py
index 902d84edef..5c96c9778b 100644
--- a/workspace_tools/toolchains/arm.py
+++ b/workspace_tools/toolchains/arm.py
@@ -30,8 +30,8 @@ class ARM(mbedToolchain):
     DIAGNOSTIC_PATTERN  = re.compile('"(?P<file>[^"]+)", line (?P<line>\d+): (?P<severity>Warning|Error): (?P<message>.+)')
     DEP_PATTERN = re.compile('\S+:\s(?P<file>.+)\n')
     
-    def __init__(self, target, options=None, notify=None):
-        mbedToolchain.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        mbedToolchain.__init__(self, target, options, notify, macros)
         
         if   target.core == "Cortex-M0+":
             cpu = "Cortex-M0"
@@ -123,16 +123,16 @@ class ARM(mbedToolchain):
 
 
 class ARM_STD(ARM):
-    def __init__(self, target, options=None, notify=None):
-        ARM.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        ARM.__init__(self, target, options, notify, macros)
         self.ld.append("--libpath=%s" % ARM_LIB)
 
 
 class ARM_MICRO(ARM):
     PATCHED_LIBRARY = False
     
-    def __init__(self, target, options=None, notify=None):
-        ARM.__init__(self, target, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        ARM.__init__(self, target, options, notify, macros)
         
         # Compiler
         self.asm  += ["-D__MICROLIB"]
diff --git a/workspace_tools/toolchains/gcc.py b/workspace_tools/toolchains/gcc.py
index fef4c03fe7..b74c1bd638 100644
--- a/workspace_tools/toolchains/gcc.py
+++ b/workspace_tools/toolchains/gcc.py
@@ -29,8 +29,8 @@ class GCC(mbedToolchain):
     CIRCULAR_DEPENDENCIES = True
     DIAGNOSTIC_PATTERN = re.compile('((?P<line>\d+):)(\d+:)? (?P<severity>warning|error): (?P<message>.+)')
     
-    def __init__(self, target, options=None, notify=None, tool_path=""):
-        mbedToolchain.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None, tool_path=""):
+        mbedToolchain.__init__(self, target, options, notify, macros)
         
         if target.core == "Cortex-M0+":
             cpu = "cortex-m0"
@@ -162,8 +162,8 @@ class GCC(mbedToolchain):
 
 
 class GCC_ARM(GCC):
-    def __init__(self, target, options=None, notify=None):
-        GCC.__init__(self, target, options, notify, GCC_ARM_PATH)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC.__init__(self, target, options, notify, macros, GCC_ARM_PATH)
         
         # Use latest gcc nanolib
         self.ld.append("--specs=nano.specs")
@@ -174,8 +174,8 @@ class GCC_ARM(GCC):
 
 
 class GCC_CR(GCC):
-    def __init__(self, target, options=None, notify=None):
-        GCC.__init__(self, target, options, notify, GCC_CR_PATH)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC.__init__(self, target, options, notify, macros, GCC_CR_PATH)
         
         additional_compiler_flags = [
             "-D__NEWLIB__", "-D__CODE_RED", "-D__USE_CMSIS", "-DCPP_USE_HEAP",
@@ -187,8 +187,8 @@ class GCC_CR(GCC):
 
 
 class GCC_CS(GCC):
-    def __init__(self, target, options=None, notify=None):
-        GCC.__init__(self, target, options, notify, GCC_CS_PATH)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC.__init__(self, target, options, notify, macros, GCC_CS_PATH)
 
 
 class GCC_CW(GCC):
@@ -196,13 +196,13 @@ class GCC_CW(GCC):
         "Cortex-M0+": "armv6-m",
     }
     
-    def __init__(self, target, options=None, notify=None):
-        GCC.__init__(self, target, options, notify, CW_GCC_PATH)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC.__init__(self, target, options, notify, macros, CW_GCC_PATH)
 
 
 class GCC_CW_EWL(GCC_CW):
-    def __init__(self, target, options=None, notify=None):
-        GCC_CW.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC_CW.__init__(self, target, options, notify, macros)
         
         # Compiler
         common = [
@@ -230,5 +230,5 @@ class GCC_CW_EWL(GCC_CW):
 
 
 class GCC_CW_NEWLIB(GCC_CW):
-    def __init__(self, target, options=None, notify=None):
-        GCC_CW.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        GCC_CW.__init__(self, target, options, notify, macros)
diff --git a/workspace_tools/toolchains/iar.py b/workspace_tools/toolchains/iar.py
index 8f935b6f3f..f6a6741d84 100644
--- a/workspace_tools/toolchains/iar.py
+++ b/workspace_tools/toolchains/iar.py
@@ -29,8 +29,8 @@ class IAR(mbedToolchain):
     
     DIAGNOSTIC_PATTERN = re.compile('"(?P<file>[^"]+)",(?P<line>[\d]+)\s+(?P<severity>Warning|Error)(?P<message>.+)')
     
-    def __init__(self, target, options=None, notify=None):
-        mbedToolchain.__init__(self, target, options, notify)
+    def __init__(self, target, options=None, notify=None, macros=None):
+        mbedToolchain.__init__(self, target, options, notify, macros)
         
         c_flags = [
             "-Oh",