Two trials were conducted with broiler chicks to determine the effects of population density on the growth, feed efficiency, and several physiological parameters associated with stress in birds. Chicks were brooded in batteries at 116, 232, 348, and 697 cm2/chick. Chicks brooded at 348 cm2/chick grew and utilized feed significantly better than those brooded at 697 cm2/chick during the first week. For maximum growth and feed efficiency, 116 cm2/chick was adequate for the first week; 232 cm2/chick was adequate during the second and third weeks. Increasing cage density significantly decreased percentage heart and spleen weights (g/100 g body weight) and plasma corticosterone at 3 weeks.