Plasma levels of luteinizing hormone (LH) and testosterone were determined by radioimmunoassay in medical students just before (Exp. 1) and after (Exp. 2) an academic examination and corresponding control periods. Before the examination (Exp. 1), the males' LH values were lower than their control levels, but there was no such difference in the females. Testosterone levels were unaffected in both sexes. There was no correlation between the values of LH and testosterone. There was, however, a significant negative correlation in the males, and an almost significant negative correlation in the females, between the preexamination testosterone values and the examination scores achieved. After the examination (Exp. 2), again the LH values were lower than the control values in the males, but not in the females, and the testosterone values were unaffected in both sexes. There was a weak positive correlation between the postexamination LH and testosterone values in the males, but not in the females. The results are in line with earlier observations suggesting that psychological stress is associated with different hormonal effects in males and females.