Although androgens act on the primate central nervous system to modulate both endocrine functions and a number of limbic-related behaviors, little is known about the anatomical location of the neurons which sequester these steroids in primates. To determine the prime location of these androgen-concentrating neurons in the forebrain of the primate, we injected three castrated female rhesus monkeys in the femoral vein with 1 microgram of 5 alpha-dihydro (1,2,4,5,6,7-3H) testosterone (3H-DHT, 107 Ci/mmole) per kg of body weight. One of these animals also received an IV injection of 100 micrograms/kg body weight of unlabeled dihydrotestosterone (DHT) to serve as a control. One hour after the injection of 3H-DHT we rapidly exsanguinated each animal. The forebrain was sliced and blocks containing the amygdala, diencephalon, frontal pole, and hippocampus were frozen and stored in liquid nitrogen until processing. The tissue was then processed for autoradiography. A specific topographic pattern of nuclear concentration of DHT or one of its metabolites was obtained in neurons of the basal hypothalamus, preoptic region, amygdala, and hippocampus. This pattern was similar to that found in rodent species.