[Undescended testis--a review]

According to registrations in several countries far too many retractile testes are falsely included in patient materials of truly undescended testes. The problem of overtreatment is so great that even with a low frequency of complications to the treatment, the netto effect on the population's fertility may become negative. The most important task for the clinician is to discern truly undescended from retractile testes. The decision has to be based on thorough clinical examination, but ultrasonography may provide objective evidence. The article presents a state-of-the-art review on experimental and clinical aspects of cryptorchidism.