The efficacy of hCG treatment was studied in 182 cryptorchid patients. The efficacy of the treatment correlated with the initial position of the testis. None of the abdominal testes reached a normal position, whereas 90% of high scrotal testes descended during the treatment. Fifty-four boys who were treated unsuccessfully with hCG and 29 untreated boys were biopsied. The biopsies were performed on 32 scrotal and 87 maldescended testes to examine the state of the organ and the effects of hCG treatment. In biopsies, the volume densities of seminiferous tubules, interstitial tissue and blood vessels were counted, and the sections screened for interstitial bleeding. Significant differences between scrotal and maldescended testes were found in all of the volume densities measured. Interstitial bleeding occurred rarely in scrotal testes, whereas in maldescended testes it was frequently apparent. hCG treatment induced a significant increase in the volume density of both interstitial tissue and blood vessels. Even though the hCG treatment induced measurable, possibly harmful, changes both in scrotal and maldescended testes, our data do not prove that hCG treatment causes permanent damage to the testis.