We performed a 5-year histopathological review of 41 consecutive cases of transitional cell carcinoma. Of these cases 8 were positive for human chorionic gonadotropin immunoperoxidase tissue staining. All tumors were grade III and stages ranged from A to D. Three patients presented with gynecomastia as the clinical manifestation of elevated serum levels of beta-human chorionic gonadotropin. These findings document the association of this phenomenon with lesions of an aggressive nature. As with the loss of cell surface antigens, the appearance of human chorionic gonadotropin within the tumor cells may be further evidence of dedifferentiation. Human chorionic gonadotropin production may be a potential marker to gauge tumor response to chemotherapy and, perhaps, a predictor of future aggressiveness and over-all progression.