Plasma testosterone (ng/ml) was measured in a group of prepuberal children with intrascrotal testes (n = 15) and in a group of prepuberal cryptorchid children (7 unilateral and 3 bilateral; n = 10) before and after stimulus with 3000IU of HCG (Group A) and with 5000IU (Group B). The serum testosterone before HCG stimulus was similar in normal (Group A: 1.10 +/- 0.03: Group B: 1.18 +/- 0.31) as well as in those of the cryptorchid children (Group A: 1 +/- 0.28; Group B: 1.19 +/- 0.36). The stimulus with 3000IU of HCG did not significantly raise the plasma testosterone in both normal (2.42 +/- 1.09) and cryptorchid children (1.70 +/- 0.5). The stimulus with 5000IU of HCG increased the plasma testosterone to 3.52 +/- 1 in normal children and 3.26 +/- 1.2 in cryptorchid children (p less than 0.05 with respect to the pre HCG values), with no difference in the response between the normal and the cryptorchid children.