A total of 320 intersex patients with a Y chromosome were classified into four groups; (1) gonadal dysgenesis, (2) asymmetrical gonadal differentiation, (3) virilizing male hermaphroditism and (4) feminizing male hermaphroditism (testicular feminization syndrome). Of these 320 cases, 98 were from the files of The Johns Hopkins Hospital and the remainder from the literature. The incidence of tumors in relation to age and clinical classification was analyzed by computer. The results were plotted for each group. It was found that the percentage of tumors rose appreciably soon after the age of puberty in the first three groups, and it was concluded that the gonads were best removed before the age of puberty. In the case of testicular feminization patients, procrastination until the age of 25 could be considered, if one were willing to assume the risk of neoplasia of about 3.6 per cent until then.