diff --git a/builder.py b/builder.py
index d48c5a16b..b60de587d 100755
--- a/builder.py
+++ b/builder.py
@@ -30,8 +30,7 @@ parser.add_option('--datadir', default='share', dest='datadir')
 parser.add_option('--mandir' , default='share/man', dest='mandir')
 
 class BuilderApp():
-    builder_filename = 'builder.txt'
-    
+
     def __init__(self, dir1, dir2, options):
         (self.source_dir, self.build_dir) = self.validate_dirs(dir1, dir2)
         if options.prefix[0] != '/':
@@ -39,7 +38,7 @@ class BuilderApp():
         self.options = options
     
     def has_builder_file(self, dirname):
-        fname = os.path.join(dirname, BuilderApp.builder_filename)
+        fname = os.path.join(dirname, environment.builder_filename)
         try:
             ifile = open(fname, 'r')
             ifile.close()
@@ -66,7 +65,7 @@ class BuilderApp():
         raise RuntimeError('Neither directory contains a builder file %s.' % BuilderApp.builder_filename)
     
     def generate(self):
-        code = open(os.path.join(self.source_dir, BuilderApp.builder_filename)).read()
+        code = open(os.path.join(self.source_dir, environment.builder_filename)).read()
         if len(code.strip()) == 0:
             raise interpreter.InvalidCode('Builder file is empty.')
         assert(isinstance(code, str))
diff --git a/environment.py b/environment.py
index ec2d73c72..173064063 100755
--- a/environment.py
+++ b/environment.py
@@ -16,6 +16,8 @@
 
 import subprocess, os.path
 
+builder_filename = 'builder.txt'
+
 class EnvironmentException(Exception):
     def __init(self, *args, **kwargs):
         Exception.__init__(self, *args, **kwargs)
diff --git a/interpreter.py b/interpreter.py
index 8969d6872..8268d2e23 100755
--- a/interpreter.py
+++ b/interpreter.py
@@ -17,6 +17,7 @@
 import parser
 import nodes
 import environment
+import os
 
 class InterpreterException(Exception):
     pass
@@ -168,6 +169,7 @@ class Interpreter():
         self.variables = {}
         self.environment = build.environment
         self.build_func_dict()
+        self.subdir = ''
 
     def build_func_dict(self):
         self.funcs = {'project' : self.func_project, 
@@ -178,7 +180,8 @@ class Interpreter():
                       'shared_library' : self.func_shared_lib,
                       'add_test' : self.func_add_test,
                       'headers' : self.func_headers,
-                      'man' : self.func_man
+                      'man' : self.func_man,
+                      'subdir' : self.func_subdir
                       }
 
     def sanity_check_ast(self):
@@ -285,6 +288,16 @@ class Interpreter():
         m = Man(args)
         self.build.man.append(m)
         return m
+    
+    def func_subdir(self, node, args):
+        self.validate_arguments(args, 1, [str])
+        prev_subdir = self.subdir
+        self.subdir = os.path.join(prev_subdir, args[0])
+        buildfilename = os.path.join(self.subdir, environment.builder_filename)
+        code = open(os.path.join(self.environment.get_source_dir(), buildfilename)).read()
+        assert(isinstance(code, str))
+        print('Going to subdirectory "%s".' % self.subdir)
+        self.subdir = prev_subdir
 
     def build_target(self, node, args, targetclass):
         for a in args: