Trials were conducted to evaluate growth rates of two age groups of young ringnecked pheasants (Phasianus colchicus) fed two dietary protein levels (28 and 18%) and at two environmental temperatures (warm and cool). Birds fed the high protein diet gained faster and more efficiently than those fed the low protein diet during the first 24 days posthatching. Beyond that time, birds gained just as well on the 18% CP diet. Heat stress slowed weight gains, more in older (45-day-old) than in younger (24-day-old) birds, and particularly when the high protein diet was fed. (