Profiles for testosterone (T), androstenedione (A), dehydroepiandrosterone (DHEA), and progesterone (P) in bovine semen were established for a group of four post-pubertal bulls by depleting the bulls' extra-gonadal sperm reserves (EGR) on three occasions at two week intervals. Each depletion consisted of 14 consecutive ejaculates combined into five pools to reduce variation and to provide adequate volume for steroid radioimmunoassay. Concentration of T and A in semen decreased significantly during depletion and reached basal concentrations. Basal concentrations were regarded as those amounts continually being produced and were considered to have been reached if there were no significant decreases in these concentrations for two or more successive pools. Testosterone concentration decreased from a mean (±SE) of 1.09 (±.17) ng/ml for the first two ejaculates (pool 1) to .26 (±.04) for ejaculates 11 to 14 (pool 5). Decreases in DHEA and P with depletion of EGR were not significant. Only T concentration was similar for pools 4 and 5, but repeatability was dependent on EGR depletion. A difference of approximately .4 ng T/ml was required to establish a significant difference among bulls in this study. Seminal T concentration decrease was not accompanied by a corresponding decrease in seminal fructose concentration nor were any other semen quality characteristics related to seminal T concentration. / M.S.