Genotyping analysis was performed for Gly146Ala polymorphism in the gene for steroidogenic factor-1 (SF-1), which is known to reduce the transactivation function by approximately 20%, in 72 cryptorchid patients and 136 control males, revealing that the Ala allele, the Ala/Gly genotype, and the Ala/Ala plus Ala/Gly genotype frequencies were significantly higher in the patients than in the control males. The results suggest that the Gly146Ala polymorphism may be a susceptibility factor for the development of cryptorchidism (CO).