As others have mentioned, I am 100% for microchipping. Even indoor kitties are regular Houdini's if they want outside badly enough. If we had known about microchipping in time, we could have saved Kuhio from being put to sleep all alone and scared at the shelter. All of our babies are chipped. Halo weighs 10 pounds, no problem. Cammie weighs 9 pounds, no problem. Pepper weighs 6 pounds, no problem. The only kitty that seems to have experienced some discomfort when we got him chipped is my sister's cat "Seymour". Seymour is over 20 pounds and the vet explained that all the scars around his neck (from his days on the street) made it a little tougher to get the needle in. But, no one ever experienced any infection or anything. Go for it! If your babies ever get away from you, your chance of being reunited with them is much increased if they are chipped.