There were some originally issues acording to the errata sheet's for the 18F67K22 dealing with the a/d offset issue. I have found that working with the latest versions of silicon that placing 1uF. tantalum filtering caps at the AVDD to AVSS cleaned up all of the noise I was experencing. I 12 of the 16 available A/D channels currently and have had no problems with the 12 bit conversions. I also use 10uF. tantalum caps as well as .1uF at all of the Vdd to Vss connections. I run the on board regulator w/5 volts on all other pins except the A/D +vref pin which is 4.096 volts.

Dave Purola,