Clinical factors were studied in a population based survey of 1,116 cases of testicular neoplasms in Victoria, Australia, between 1950 and 1978. The ratio of right to left sided tumours was 54:46, but the left side predominated among sarcomas (P = 0.006), and in older men. The relative risk (RR) for men with unilateral maldescent was 15 (CI 10-23) and for men with bilateral maldescent 33 (CI 20-55) (odds ratio 1.4, CI 0.5-4, P = 0.7). Calculations per testis in men with unilateral maldescent showed an elevated risk for both the maldescended testis (RR 28, CI 19-41, P less than 0.0001) and the normally descended testis (RR 3, CI 1.2-6, P = 0.04). The RR for men with abdominal maldescent was 55 (CI 36-83) compared to 7 (CI 4-11) for those with inguinal maldescent (odds ratio 8, CI 3-20, P less than 0.0001). Seminomas were more common than nonseminomas (NSGCT) in men with a history of maldescent (odds ratio 1.7, CI 1.1-3, P = 0.02) and also among corrected cryptorchids compared to uncorrected (P = 0.005). Seminomas were diagnosed at an earlier median age in men with corrected cryptorchid testes compared to uncorrected (P = 0.03) and in men with corrected cryptorchid testes compared to normally descended (P = 0.001). Maldescent was also associated with hernia (P = 0.04). Twenty-eight per cent of patients recorded a history of trauma with a higher proportion among NSGCT than among seminomas (P = 0.03). Prior malignancies were reported in nine patients, compared to 3.6 expected; prostate cancer (2) and malignant melanoma (2) were the greatest contributors to the excess.