This study investigated the effects of cold and exercise in the cold on the physiological and cognitive responses of 11-12-year-old boys. Children were dressed in sweat suits and exposed to cold (CD, 7°C), cool (CL, 13°C), and neutral (N, 22°C) environments for 110 minutes, with 10 minutes of light exercise (1 watt · kg body wt ) midway through the exposure. A 30-minute "recovery" in neutral conditions followed each session. Session order was randomized. Rectal temperature (Tre) decreased significantly more in CD compared to CL and N, and continued to decrease during the recovery period. Chest skin temperature (Tch) was significantly different between conditions and remained stable even in CD, despite the decrease in Tre. Tch returned to prechamber values during the recovery period. Hand temperature (Th) decreased during CL and CL, and remained significantly lower than prechamber values following the recovery. Exercise heart rate was lower in the CD and CL(115 ± 13 and 119 ± 20 beats · min ) compared to N (130 ± 17 beats · min ). No differences were observed in oxygen consumption between sessions. No differences were also observed between sessions in cognitive performance on language and math tests. It was concluded that while the study conditions did not appear to affect cognitive capacity in boys, they proved sufficient to disturb core temperature. This disturbance was not corrected 30 minutes following cold exposure. Am. J. Hum. Biol. 9:39-49 © 1997 Wiley-Liss, Inc.