The feeding behaviour of two litters of four kittens each has been studied. Düring the first few days of life each kitten gradually establishes ownership of one teat, and then rarely feeds from any teat but its own. One kitten was exceptional in establishing ownership of two teats. Teat constancy is well maintained until the kittens become active enough to leave the nest and feed independently of the mother at the age of about 32 days. From this age until the end of lactation, although teat constancy is less rigidly maintained, it doet not vanish completely. The factors which bring about this reduction in teat constancy are discussed. Some incidental observations on the behaviour of the females towards the kittens of the foreign litter are included. The clues which a kitten may utilise in recognising its own teat and the biological significance of teat constancy are briefly considered.