Among the antihypertensives currently in use, the sympatholytic drugs (e.g., central alpha-agonists, beta-blockers) and diuretics are most commonly associated with sexual side effects. Previous reports of sexual dysfunction associated with these drugs have been based entirely on retrospective and self-report data. This is the first study to date to investigate beta-blocker effects on sexual function by means of physiological (NPT), subjective, and hormonal measures. Four beta-blockers with different ancillary properties (atenolol, metoprolol, pindolol, propranolol) were evaluated in a placebo-controlled, double-blind, Latin-square design. Thirty healthy male volunteers received, in counterbalanced order, each of the four drugs and 1 week of placebo testing. Significant drug effects on both total and free testosterone were found during treatment with all four beta-blockers, although it appeared that the nonselective drugs (pindolol, propranolol) were associated with the greatest reduction in testosterone. No significant effects were found on measures of cortisol or cholesterol. Analysis of NPT and self-report data yielded inconclusive results, perhaps due to the confounding effects of sleep disruption and the brief duration of treatment in this study. Inspection of individual records, however, suggested that some subjects may be especially vulnerable to sexual dysfunction in association with propranolol.