Nicholas turkeys at the age of 15 to 16 weeks were fasted for 24 hours in a moderate environment and then subjected to acute heat exposures of various dry-bulb and wet-bulb temperatures (T^u, and T^jj). Total feed intake was not influenced by T^^ of 32*' C, 36"* C or 40° C (P > 0.10), although differences existed in dynamic feeding profiles. Total heat production rate (THP) varied quadratically with T^^, and respiratory quotient (RQ) decreased linearly with T^u,. The lower RQ values at the higher T^i^ levels may have resulted from reduced feed assimilation. No differences were detected on feed intake, THP, and RQ between the two T^j, levels at each T^^. A THP-based temperature-humidity index, 0J4T^^ + 0.26T^l,, was derived for the turkeys. In addition, T^^ and T^j, had 56% and -44% relative importance on latent heat loss, but -32% and 68% relative importance on sensible heat loss.