My dog, Star, is a rescue dog who was chipped three years before I got her (24petwatch.com). I did the blood work and vaccine in Dec 2008, figuring all would be ok, since she was chipped. Ahh - then I learned they need to be able to READ the chip...and 24petwatch ones (manufactured by Bayer) are NOT ISO.
However, my vet kindly called Bayer and got them to send her a reader, which I'll purchase from them -- at cost, for $210 -- so Star should be ok.
Hopefully, we'll be fine. Interestingly enough, I checked the Univ of KS rabies Web site (
http://www.vet.k-state.edu/depts/dmp/service/rabies/) where you can search by chip number to verify status and they have Star's microchip number in the system with her results.
Just wanted to advise that even if the chip isn't ISO, there may be other options, though they'll cost a bit!