Four hundred eighty-eight lesions from 456 patients were surveyed for the production of hCG using the immunoperoxidase technique. HCG immunoreactivity was found in 9.1% of the total number of cases studied. The 10% of ovarian cancers expressing hCG included serous, endometrioid, and germ cell tumors. Eighteen point nine percent of neoplastic cervices were positive for hCG; the highest rate of expression was in invasive cancers. Eighteen point nine percent of endometrial cancers were hCG positive; poorly differentiated tumors had the highest percent of marker expression. The significance of "ectopic" hCG expression in nontrophoblastic gynecologic neoplasms is discussed.