Both partners of 455 infertile couples seen consecutively were evaluated. When indicated the female partners were treated. Six semen specimens from each male subject were analyzed. A varicocele was diagnosed in 23.7 per cent of the men. More than 60 per cent of the men with a varicocele had sperm counts less than 40 million per ml., while 67 per cent without a varicocele had sperm counts more than 40 million per ml. The mean and total sperm counts of men with a varicocele were significantly lower than those without a varicocele. However, the pregnancy rates were not significantly different. The pregnancy rate was 46 per cent in couples whose male partners underwent a varicocelectomy, not significantly different from the pregnancy rate achieved in couples when the varicoceles were not corrected surgically (51 per cent). Varicocelectomy resulted in improvement in sperm count only when preoperative counts were more than 10 million per ml. Pregnancy rates for couples in which a varicocelectomy did or did not result in improvement in sperm count or motility were identical (45.1 and 45.5 per cent, respectively). These findings suggest that in male partners of infertile couples the presence of a varicocele is associated with compromised semen quality but not with diminished fertility when the female partners are treated. This observation emphasizes the importance of considering infertility as a problem of a couple, rather than a specific disorder of one of the partners.