Thanks very much to everyone who helped me with this. I got things *kinda* working (transmit only for now) running at 4.5v, cts<->rts and dsr<->dtr, and with 200 Ohms from the pic xmit pin to the rs-232 Rx line. Current unsolved mystery is why it only works reliably with the scope's ground clip attached to my circuit ground (with scope probe unattached.)... Cheers, Dan