The nitrogen requirements of cats during gestation and lactation were determined. Purified diets containing 200, 250, or 300 g protein (N 6.25)/kg diet, calculated ME = 20 kJ/g) and ≥ 1.5 times the minimal essential amino acid requirement of the growing kitten were fed for ≥ one month before mating and through gestation and lactation. Results during gestation showed that there were no significant differences among treatments in number and size of kittens at birth and suggested that 200 g protein/kg diet was adequate. Treatments had little effect on kitten weight gains at week one or two. By the third week, kitten weight gains were significantly higher for the higher levels of dietary protein. Queens fed the 200 g protein/kg diet had a lower PCV at 6 weeks lactation than queens fed the 250 or 300 g protein/kg diet. Essential amino acid concentrations in plasma at 3 week lactation indicated that two to five of the essential amino acids may have been limiting, even though they were all added in the diet at 1.5 times that of the kitten growth requirement. Results suggest that the protein requirement of the queen during gestation is not greater than 200 g protein/kg diet and the requirement during lactation appears to be between 250 and 300 g protein/kg diet containing 250 g fat/kg diet.