This study was carried out at the Experimental Farm of Animal Physiology Research Lab, Faculty of Agriculture, Cairo University, during the summer season of 2004. The objective was to assess the relevant physiological responses and growth performance of Egyptian buffalo-calves to artificial constant severe heat stress (40°C, 87.5 % RH, lab A), comfort (25 °C and 64.5% RH, lab B). Eight buffalo-calves were used (4 in each lab), their age and live body weight were 6 months and about 119 kg, respectively. Animals in both labs were assessed under their conditions for two times (trial 1 and trial 2), each one continued for one month, between them animals spent fifteen days outdoors. Then, they were slaughtered. Heat stress caused reduction in the weight of the visceral organs. Fast BW and empty BW were decreased. Heat stress caused decrease in the length of small and large intestines and appendix. Fat % in the lean meat was reduced due to heat stress in both longissimus dorsi and semitendinosus muscles.