Inheritance and testicular cancer.

Statistical analysis of published data on the age of onset of germ cell tumours of the testis and of the prevalence of bilateral disease in familial and general cases suggest the following: 1. Patients with bilateral disease carry the same genetic predisposition as familial cases. 2. Males with the hereditary predisposition develop none, unilateral or bilateral tumours in the proportions 55%, 38% and 7% respectively. 3. One-third of all testis cancer patients are genetically predisposed to the disease. 4. The 2.2% risk to brothers of cases as reported elsewhere can be accounted for by the homozygous (recessive) inheritance of a single predisposing gene.