1. Four rearing temperature regimes (15, 20, 25, 30 °C) and three feeding schedules (ad libitum, restricting to the ad libitum intake of the 12th week and feeding 70% of this rate) were carried out with layer replacement pullets to 170 d of age. From this age, during lay, birds were kept at either 21 °C or on a 24-h cycle of 21 for 18 h and 28 °C for the 6 h before lights out. Both a white and a brown egg-laying strain were used. 2. Body weight at 169 d of age varied from, on average, 1409 g (15 °C, ad libitum) to 943 g (30 °C, 70% schedule) for the white strain and 1947 to 1250 g for the same treatments respectively for the brown strain. Sexual maturity was considerably delayed by the 70% feeding schedule, only slightly by rearing at 30 °C. - 3. Rearing at 30 °C tended to depress subsequent egg output. The 70% feeding schedule at least maintained egg output compared with birds fed ad libitum in rearing. 4. There was a highly significant effect of temperature treatment during lay on food intake. The reduction in food intake due to the 21–28 °C cycle, however, appeared small.