Crossing into the States you need an up to date distemper and rabies vaccination for your dog. We have taken our 6 year old Yellow Lab into the States and Mexico and never had a problem. As I understand it, if you don't have up to date shots for your pooch Canada Customs can refuse your pet re entry into the country until he has been quarentined for 30 days. I always have up to date distemper, rabies and parvo shots and carry the vet's certificate with me although I have never been asked for them.