Commercial broiler males were used to evaluate body temperature response to heat stress and its relationship to gain, feed consumption, and feed conversion ratio. Individual gain, feed consumption, and feed conversion ratio were obtained from 28 to 49 d in a heat stress environment (32 C) and compared to a 21 C environment. Body temperatures were measured at 28, 35, and 42 d, then daily from 43 to 48 d, and correlated with 28 to 49 d gain, feed consumption, and feed conversion ratio. Feather cover was measured at 51 d of age as a percentage of BW. Initial 28-d body temperature was not significantly different between 21 and 32 C. Body temperature was significantly higher in the 32 C environment after 7 d of heat stress and was significantly higher than at 21 C at all points through 21 d of heat stress, with mean differences ranging from 0.5 to 1.0 C. Feather weight as a percentage of BW was significantly greater in the 21 C environment (6.22%) than the 32 C environment (5.03%). Mortality was not affected by the heat stress environment. Correlations between body temperature and gain, feed consumption, and feed conversion ratio were low and nonsignificant for most periods in the 21 C environment. In the 32 C environment, body temperature was significantly correlated with gain, feed consumption, and feed conversion ratio after 7 d of heat stress, with mean correlations of -0.40 for gain, -0.31 for feed consumption, and 0.24 for feed conversion ratio in Replicate 1 and -0.44 for gain, -0.40 for feed consumption, and 0.43 for feed conversion ratio in Replicate 2.