Plasma testosterone concentration was decreased in 10 patients combining varicocele with sexual inadequacy (mean 346.2 ng/100 ml) against normal concentration observed in 23 men with varicocele without sexual disturbances (mean 567.8 ng/100 ml) and in 31 patients with pure psychogenic impotence (mean 581.6 ng/100 ml). There was a significant inverse linear correlation between age and plasma testosterone concentration in the varicocele patients (r= minus 0.56, P smaller than 0.01) in contrast to the absence of such correlation in normal men or in patients with psychogenic impotence of the same age range. The secretion products of the secondary sex glands were more often in the lower range in the ejaculates of men combining varicocele with sexual disturbance (P smaller than 0.02), proving the decreased testosterone level to induce a deficient function of these glands. Plasma testosterone levels normalized after surgical correction in varicocele patients with a low preoperative concentration. Since adequate surgical or hormonal treatment resulted in complete recovery of sexual potency in the majority of patients with varicocele and sexual inadequacy, it is suggested that the decreased testosterone production might have contributed to the impairment of sexual function.