diff --git a/src/Ophis/CmdLine.py b/src/Ophis/CmdLine.py
index 6beb174..5cf80b3 100644
--- a/src/Ophis/CmdLine.py
+++ b/src/Ophis/CmdLine.py
@@ -19,7 +19,7 @@ print_pass = False
 print_ir = False
 print_labels = False
 
-infile = None
+infiles = None
 outfile = None
 
 
@@ -30,12 +30,15 @@ def parse_args(raw_args):
     global warn_on_branch_extend
     global print_summary, print_loaded_files
     global print_pass, print_ir, print_labels
-    global infile, outfile
+    global infiles, outfile
 
     parser = optparse.OptionParser(
         usage="Usage: %prog [options] srcfile outfile",
         version="Ophis 6502 cross-assembler, version 2.0")
 
+    parser.add_option("-o", default=None, dest="outfile",
+                      help="Output filename (default 'ophis.bin')")
+
     ingrp = optparse.OptionGroup(parser, "Input options")
     ingrp.add_option("-u", "--undoc", action="store_true", default=False,
                      help="Enable 6502 undocumented opcodes")
@@ -66,17 +69,13 @@ def parse_args(raw_args):
 
     (options, args) = parser.parse_args(raw_args)
 
-    if len(args) > 2:
-        parser.error("Too many files specified")
-    if len(args) == 1:
-        parser.error("No output file specified")
     if len(args) == 0:
-        parser.error("No files specified")
+        parser.error("No input files specified")
     if options.c02 and options.undoc:
         parser.error("--undoc and --65c02 are mutually exclusive")
 
-    infile = args[0]
-    outfile = args[1]
+    infiles = args
+    outfile = options.outfile
     enable_collapse = options.enable_collapse
     enable_branch_extend = options.enable_branch_extend
     enable_undoc_ops = options.undoc
diff --git a/src/Ophis/Frontend.py b/src/Ophis/Frontend.py
index f8176ce..8bade2e 100644
--- a/src/Ophis/Frontend.py
+++ b/src/Ophis/Frontend.py
@@ -371,9 +371,12 @@ def parse_file(ppt, filename):
         return IR.NullNode
 
 
-def parse(filename):
+def parse(filenames):
     """Top level parsing routine, taking a source file name
-    and returning an IR list."""
+    list and returning an IR list."""
     global templabelcount
     templabelcount = 0
-    return parse_file("<Top Level>", filename)
+    nodes = [parse_file("<Top Level>", f) for f in filenames]
+    if len(nodes) == 1:
+        return nodes[0]
+    return IR.SequenceNode("<Top level>", nodes)
diff --git a/src/Ophis/Main.py b/src/Ophis/Main.py
index f66bf08..2513d23 100644
--- a/src/Ophis/Main.py
+++ b/src/Ophis/Main.py
@@ -18,10 +18,10 @@ import Ophis.CmdLine
 import Ophis.Opcodes
 
 
-def run_all(infile, outfile):
-    "Transforms the source infile to a binary outfile."
+def run_all(infiles, outfile):
+    "Transforms the source infiles to a binary outfile."
     Err.count = 0
-    z = Ophis.Frontend.parse(infile)
+    z = Ophis.Frontend.parse(infiles)
     env = Ophis.Environment.Environment()
 
     m = Ophis.Passes.ExpandMacros()
@@ -57,6 +57,8 @@ def run_all(infile, outfile):
         try:
             if outfile == '-':
                 output = sys.stdout
+            elif outfile is None:
+                output = file('ophis.bin', 'wb')
             else:
                 output = file(outfile, 'wb')
             output.write("".join(map(chr, a.output)))
@@ -79,7 +81,7 @@ def run_ophis(args):
         Ophis.Opcodes.opcodes.update(Ophis.Opcodes.c02extensions)
 
     Ophis.CorePragmas.reset()
-    run_all(Ophis.CmdLine.infile, Ophis.CmdLine.outfile)
+    run_all(Ophis.CmdLine.infiles, Ophis.CmdLine.outfile)
 
 
 if __name__ == '__main__':