I've had 4 kitties chipped so far. None of them required any kind of anesthesia. Three of them didn't put up a fuss at all. They were the 3 small females. The big male (17 pounds) acted like it hurt him some. The vet said it is because he is a big baby and because he had a lot of scars on his neck from his days as a street fighter before we nabbed him and turned him into a house cat. They've all been chipped for over a year now and have had no adverse reactions.