The authors determined the prevalence of hyperprolactinemia in impotent men in a community setting and assessed the cost of case detection with routine estimation of serum prolactin. They recruited 299 consecutive patients with impotence and determined the hormonal levels (prolactin, luteinizing hormone, follicle-stimulating hormone, and testosterone). Pituitary gland imaging was done when the prolactin level was elevated. Simultaneous prolactin and testosterone levels were available for 212 patients. Three patients (1.4%) had elevated prolactin levels but none had pituitary tumor. Two of these had low testosterone levels. Overall, 51 patients (24.1%) had low testosterone levels. Cost of selective prolactin estimation in patients with low testosterone levels resulted in a net saving of $2,574 per case detected. The authors conclude that the prevalence of hyperprolactinemia in impotence is low. Routine measurement of prolactin levels in impotence is not indicated. Selective determination in patients with low testosterone reduces the cost of diagnostic evaluation.