Little is known about the influence of Telazol on cortisol or of anesthetic agents on immunological measures, and reports of ketamine's effect on cortisol are inconsistent. We measured effects of Telazol, ketamine and blood sampling on cortisol in male rhesus macaques and male savannah baboons. We also obtained leukocyte counts in the macaques. In macaques, Telazol reduced cortisol in the morning but not in the afternoon; ketamine had no effect on cortisol in these animals. In baboons, cortisol changed little post-Telazol but increased post-ketamine. In macaques, lymphocyte numbers decreased following afternoon injection of Telazol, ketamine or saline. The injection and blood sampling process increased cortisol levels in monkeys not trained to extend an arm but exerted no effect on cortisol in trained macaques. Thus, the animals' physiological responses to blood sampling and immobilization are influenced by such variables as anesthetic agent, species, time of day, and familiarity with the blood sampling process.