To evaluate the effect of antihypertensive treatment on sexual activity, 90 hypertensive men, aged 40 to 49 years, all married and without history of sexual dysfunction were treated with 100 mg of atenolol or 20 mg of lisinopril for 16 weeks, according to a double-blind, randomized, cross-over design. During the first month of therapy, sexual activity, assessed as number of sexual intercourse episodes per month, significantly declined with both atenolol (from 7.8 +/- 4.3 to 4.5 +/- 2.8, P < .01 v placebo) and lisinopril (from 7.1 +/- 4.0 to 5.0 +/- 2.5, P < .05 v placebo). Ongoing with the treatment, sexual activity tended toward recovery in the lisinopril (7.7 +/- 4.0 sexual intercourse episodes per month, P = NS v placebo), but not in the atenolol group (4.2 +/- 2.8, P < .01 v placebo), with a statistically significant difference between the two drugs (P < .01). The percentage of patients who complained of sexual dysfunction symptoms was significantly higher in the atenolol- than in the lisinopril-treated group (17% v 3%, P < .05). These findings suggest that atenolol induces a chronic worsening of sexual activity, whereas lisinopril causes only a temporary decline.