diff --git a/ll.py b/ll.py
index ffe3077..4e4bd88 100644
--- a/ll.py
+++ b/ll.py
@@ -60,6 +60,8 @@ Gep = namedtuple('Gep', ['base_ty', 'oper_ty', 'oper', 'steps'])
 Zext = namedtuple('Zext', ['from_ty', 'oper', 'to_ty'])
 Ptrtoint = namedtuple('Ptrtoint', ['pointer_ty', 'oper', 'to_ty'])
 
+CallResult = namedtuple('CallResult', ['val'])
+
 Ret = namedtuple('Ret', ['ty', 'oper'])
 Br = namedtuple('Br', ['label'])
 Cbr = namedtuple('Cbr', ['ty', 'oper', 'then_label', 'else_label'])
@@ -87,12 +89,19 @@ def oper2s(operand):
         return str(operand.val)
     elif isinstance(operand, Id):
         return '%' + operand.val
+    elif isinstance(operand, Gid):
+        return '@' + operand.val
     else:
         # TODO
         print('oper2s: Unknown operand: {}'
               .format(operand))
 
 
+def tyopers2s(ty_oper_list):
+    return ', '.join('{} {}'.format(ty2s(ty), oper2s(oper))
+                     for ty, oper in ty_oper_list)
+
+
 def insn2s(insn):
     if isinstance(insn, Binop):
         return ('{} {} {}, {}'
@@ -102,6 +111,10 @@ def insn2s(insn):
         return ('icmp {} {} {}, {}'
                 .format(insn.cnd, ty2s(insn.ty),
                         oper2s(insn.left), oper2s(insn.right)))
+    elif isinstance(insn, Call):
+        return ('call {} {} ({})'
+                .format(ty2s(insn.return_ty), oper2s(insn.callee),
+                        tyopers2s(insn.arguments)))
     elif isinstance(insn, Bitcast):
         return ('bitcast {} {} to {}'
                 .format(ty2s(insn.from_ty), oper2s(insn.oper),
@@ -114,6 +127,9 @@ def insn2s(insn):
         return ('ptrtoint {}* {} to {}'
                 .format(ty2s(insn.pointer_ty), oper2s(insn.oper),
                         ty2s(insn.to_ty)))
+    elif isinstance(insn, CallResult):
+        return ('<<internal>>: function return {}'
+                .format(insn.val))
     else:
         # TODO
         print('insn2s: Unknown insn: {}'
diff --git a/stepper.py b/stepper.py
index 0dc4519..e74f166 100644
--- a/stepper.py
+++ b/stepper.py
@@ -20,7 +20,8 @@ def warn(msg):
 def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, memory,
          tdecs, fdecs, call_res):
     if len(insns) == 0:
-        return terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory)
+        return terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory,
+                         call_res)
     ssa_target, next_insn = insns[0]
     insns_rest = insns[1:]
 
@@ -51,6 +52,40 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, memory,
         # TODO
         print('icmp {} {}, {}'
               .format(cnd,  left_v, right_v))
+    elif isinstance(next_insn, ll.Call):
+        callee = next_insn.callee
+        arguments = next_insn.arguments
+
+        if not isinstance(callee, ll.Gid):
+            err('Cannot call anything but global identifiers: {}'
+                .format(ll.oper2s(callee)))
+            return insns_rest, terminator, blocks, stack_frames, ssa_env, memory, call_res
+
+        arguments_v = [eval_oper(oper, ssa_env, global_env)
+                       for ty, oper in arguments]
+
+        try:
+            function = fdecs[callee.val]
+        except KeyError:
+            err('Could not find function {} in environment:\n{}'
+                .format(callee.val, fdecs.keys()))
+            return insns_rest, terminator, blocks, stack_frames, ssa_env, memory, call_res
+
+        parameters = function.parameters
+        print('call @{} ({})'
+              .format(callee.val,
+                      ', '.join('%{} <- {}'.format(par[1], arg)
+                                for par, arg in zip(parameters, arguments_v))))
+        child_insns = function.body.first_block.insns
+        child_terminator = function.body.first_block.terminator
+        child_blocks = function.body.named_blocks
+        child_stack_frames = [(insns_rest, terminator, blocks, ssa_env)] + stack_frames
+        child_ssa_env = {par[1]: arg for par, arg in zip(parameters, arguments_v)}
+        child_memory = memory
+        child_call_res = [ssa_target] + call_res
+        return (child_insns, child_terminator, child_blocks, child_stack_frames,
+                child_ssa_env, child_memory, child_call_res)
+
     elif isinstance(next_insn, ll.Bitcast):
         oper = next_insn.oper
         from_ty = next_insn.from_ty
@@ -81,6 +116,8 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, memory,
         # TODO
         print('ptrtoint {}* {} to {}'
               .format(ll.ty2s(pointer_ty), oper_v, ll.ty2s(to_ty)))
+    elif isinstance(next_insn, ll.CallResult):
+        res = next_insn.val
     else:
         err('Unknown LLVM instruction: {}'
             .format(next_insn))
@@ -95,10 +132,10 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, memory,
                   .format(ssa_target, res))
             ssa_env[ssa_target] = res
 
-    return insns_rest, terminator, blocks, stack_frames, ssa_env, memory, None
+    return insns_rest, terminator, blocks, stack_frames, ssa_env, memory, call_res
 
 
-def terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory):
+def terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory, call_res):
     def clear_block_from_ssa_env(insns, ssa_env):
         for (id, insn) in insns:
             if id is not None and id in ssa_env:
@@ -117,17 +154,21 @@ def terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory):
         # TODO
         print('Returning {}'
               .format(oper_v))
+
         if len(stack_frames) == 0:
-            new_insns = []
+            new_insns = [(None, ll.CallResult(oper_v))]
             new_terminator = None
             new_blocks = {}
             new_ssa_env = ssa_env
             new_stack_frames = []
+            new_call_res = []
         else:
             new_insns, new_terminator, new_blocks, new_ssa_env = stack_frames[0]
+            new_insns = [(call_res[0], ll.CallResult(oper_v))] + new_insns
             new_stack_frames = stack_frames[1:]
+            new_call_res = call_res[1:]
         return (new_insns, new_terminator, new_blocks, new_stack_frames,
-                new_ssa_env, memory, oper_v)
+                new_ssa_env, memory, new_call_res)
     elif isinstance(terminator, ll.Br):
         label = terminator.label
         next_block = blocks[label]
@@ -144,7 +185,7 @@ def terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory):
               .format(label))
 
         return (new_insns, new_terminator, blocks, stack_frames,
-                ssa_env, memory, None)
+                ssa_env, memory, call_res)
     elif isinstance(terminator, ll.Cbr):
         ty = terminator.ty
         if ty != ll.SimpleType.I1:
@@ -168,7 +209,7 @@ def terminate(terminator, blocks, stack_frames, ssa_env, global_env, memory):
               .format(operand_v, label))
 
         return (new_insns, new_terminator, blocks, stack_frames,
-                ssa_env, memory, None)
+                ssa_env, memory, call_res)
     else:
         err('Unknown LLVM terminator: {}'
             .format(terminator))
@@ -241,15 +282,17 @@ def gogo():
     data = r'''
 define i64 @tigermain (i64 %U_mainSL_8, i64 %U_mainDummy_9) {
     %a = add i64 3, 5 ; please be 8
-    %c = icmp eq i64 %a, 9
-    br i1 %c, label %L1, label %L2
+    %c = icmp eq i64 %a, 8
+    br i1 %c, label %L1, label %L1
 L1:
-    %b = add i64 %a, %a
+    %b = call i64 @f (i64 7, i64 %a)
     ret i1 %c
-L2:
-    %d = add i64 %a, 1
-    %e = add i64 10, %d
-    ret i64 %e
+}
+
+define i64 @f (i64 %x, i64 %y) {
+    %a = mul i64 2, %y
+    %b = mul i64 %x, %a
+    ret i64 %b
 }
 '''
 
@@ -269,7 +312,7 @@ L2:
     ssa_env = {}
     # TODO: memory structure has not been decided yet
     memory = [None]
-    call_res = None
+    call_res = []
 
     while True:
         (insns, terminator, blocks,
@@ -282,7 +325,7 @@ L2:
             print('Stepping done! Final ssa_env:\n{}'
                   .format(ssa_env))
             print('Program resulted in {}'.
-                  format(call_res))
+                  format(insns[0][1].val))
             break