Male hamsters were tested for copulatory behavior (CB) with receptive females, for investigatory responses to the females' ano-genital region (A/G), and for attraction to female hamster vaginal secretion (FHVS). After castration, the males received Silastic capsules containing one of two doses of testosterone (T), 5 alpha-dihydrotestosterone (DHT), estradiol (E2) or DHT + E2, and the maintenance of their copulatory and chemoinvestigatory responsiveness was assessed during weekly tests for the next month. The major findings were: (1) T thresholds for the maintenance of CB were lower than they were for the maintenance of A/G behavior and FHVS attraction; (2) DHT + E2 or DHT alone were more effective in maintaining A/G and FHVS attraction than was E2 alone; (3) DHT + E2 or DHT alone maintained ejaculatory behavior in some animals but E2 did not; (4) the posttreatment maintenance of normal ejaculation latencies and intromissions to ejaculation shown by intact and T-treated males was not demonstrated by males receiving DHT or DHT + E2. These results are consistent with the hypothesis that copulatory and chemoinvestigatory behaviors may be subserved by distinct neuroendocrine mechanisms in male hamsters.