Mixed sex, commercial broiler chickens were grown at three environmental temperatures: 15.6, 21.1, and 26.7 C. Starting at 35 days, body weights and feed conversions were measured at 3- to 5-day intervals to 55 days of age. Both body weights and feed conversions were linear with age over the time range indicated. The growth rates at 26.7 C were 6% less at 3 5 days and 10% less at 55 days than at 15.6 C. When equated for body weight differences, there was no difference in feed conversion between broilers grown at 21.1 and 26.7 C. Birds grown at 15.6 C consumed more feed per unit of weight than at the other two temperatures. At 49 days of age, the birds grown at 15.6 C required 16% more feed than those grown at 26.7 C; however, when weights were equated at 2000 g, those grown at 15.6 C required only 3% more feed than those grown at 26.7 C.