Data on body weight of pure-bred kittens (Maine Coon, Norwegian Forest Cat, Birman, Persian, Siamese/Oriental Shorthair Cat) from birth (n 245) to 12 weeks of age (n 135) were obtained from breeders. Absolute birth weight (in g) was higher in larger breeds than in smaller breeds, whereas relative birth weight (in % of mature female weight) tended to be higher in smaller breeds (Maine Coon 115 g, 2·3 %; Norwegian Forest Cat 106 g, 2·7 %; Birman 97 g, 2·8 %; Siamese 92 g, 2·8 %; Persian 82 g, 3·2 %). Relative birth weight was lower than that described in the literature for colony cats. Relative litter weight was highest in Norwegian Forest Cats (14·6 (sd 1·8) %; n 10) and lowest in Birmans (8·8 (sd 3·1) %, n 7; P < 0·05); the other breeds were in-between (11·9 (sd 2·0) %; n 19). Absolute growth was faster in larger breeds than in smaller breeds. In relation to expected mature weight, there was good agreement with data from colony cats but no clear-cut effect of breed size. There appeared to be a trend to an earlier onset of sexual dimorphism in larger breeds.