diff -r 53fc7f59c7bb Lib/test/test_struct.py
--- a/Lib/test/test_struct.py	Sat Jun 23 20:28:32 2012 +0200
+++ b/Lib/test/test_struct.py	Sat Jun 23 23:39:25 2012 +0300
@@ -572,6 +572,16 @@
         s = struct.Struct('i')
         s.__init__('ii')
 
+    def test_sizeof(self):
+        self.assertGreater(sys.getsizeof(struct.Struct('BHILfdspP')),
+                           sys.getsizeof(struct.Struct('B')))
+        self.assertGreaterEqual(sys.getsizeof(struct.Struct('123B')),
+                                sys.getsizeof(struct.Struct('B')))
+        self.assertGreaterEqual(sys.getsizeof(struct.Struct('B' * 123)),
+                                sys.getsizeof(struct.Struct('123B')))
+        self.assertGreaterEqual(sys.getsizeof(struct.Struct('123xB')),
+                                sys.getsizeof(struct.Struct('B')))
+
 def test_main():
     run_unittest(StructTest)
 
diff -r 53fc7f59c7bb Modules/_struct.c
--- a/Modules/_struct.c	Sat Jun 23 20:28:32 2012 +0200
+++ b/Modules/_struct.c	Sat Jun 23 23:39:25 2012 +0300
@@ -1752,6 +1752,19 @@
     return PyLong_FromSsize_t(self->s_size);
 }
 
+static PyObject *
+s_sizeof(PyStructObject *self, void *unused)
+{
+    Py_ssize_t res;
+    formatcode *code;
+
+    res = sizeof(PyStructObject) + sizeof(formatcode);
+    for (code = self->s_codes; code->fmtdef != NULL; code++) {
+        res += sizeof(formatcode);
+    }
+    return PyLong_FromSsize_t(res);
+}
+
 /* List of functions */
 
 static struct PyMethodDef s_methods[] = {
@@ -1760,6 +1773,8 @@
     {"unpack",          s_unpack,       METH_O, s_unpack__doc__},
     {"unpack_from",     (PyCFunction)s_unpack_from, METH_VARARGS|METH_KEYWORDS,
                     s_unpack_from__doc__},
+    {"__sizeof__",      (PyCFunction)s_sizeof, METH_NOARGS,
+     "Returns size in memory, in bytes"},
     {NULL,       NULL}          /* sentinel */
 };