In a cohort of Danish boys characterized by (1) being born between 1941 and 1957, (2) having attended schools in a defined area of Denmark, and (3) having a school health record available, 183 were registered in the Danish Cancer Registry with testicular cancer diagnosed before January 1, 1985. We selected 366 age- and sex-matched controls from the same cohort. Using information recorded by school physicians, we performed logistic regression analyses to estimate the relative risks (RR) associated with various genital anomalies. We found the risk for testicular cancer to be raised for men with a history of cryptorchidism [RR = 5.2; 95% confidence interval (CI) = 2.1-13.0], inguinal hernia (RR = 1.8; 95% CI = 0.9-3.7), hypospadias (RR = 4.2; 95% CI = 0.4-42.7), and hydrocele (RR = 2.4; 95% CI = 0.6-9.0). We observed no decrease in the risk associated with cryptorchidism after correction of the maldescent in early childhood. The RR of testicular cancer in the contralateral, normally descended testis in unilateral cryptorchid men was increased to 3.6. The results add to the growing evidence for a common causal factor for both testicular cancer and cryptorchidism and support the findings from other studies of associations between other genital anomalies involving the closure of the processus vaginalis and the risk of testicular cancer.