PurgeComm It has been a while since I worked with 422, but if you are concerned about receiving the output in the input, I would still code for ignoring any message you sent out. WIN32 just doesn't give you enough control to know when a message has been fully sent out of the comm port. You only know when output buffer is empty. There still could be characters waiting on the FIFO. But, if you are just looking to kill any characters in the input buffer, PurgeComm works great. Tim Smith I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?