I have scoped the output of the transmitter, no problem with that. To test the circuit I have a PIC16F877A transmitting:

pause 500 'make sure receiver has time to boot
let value = 1
loop:
serout portb.7, 1, [value]
pause 100
goto loop

and a PIC 16F870 receiver:

loop:
serin portb.7, 1, [value] 'get input
high led
serout portb.0, 1, [value] 'send to pin to compare waves
low led
goto loop

The led never flashes so its just sat waiting for input which it never sees, though the scope sees a nice clean signal on the input pin.

I have noted all the points Mr E mentioned. I have tried it on lots of pic types, and various pins, I have included "modedefs.bas", I have a 10k resistor from TX pin to gnd, no comparators to worry about.

I am going to try disabling the A/D before receiving data, but cant see this making a difference, since I'm using port B

regards

Bob...