Hyperthecosis of the ovaries in a woman with a placental site trophoblastic tumor. Rapidly increasing testosterone levels were observed in a patient presenting with sudden onset of virilization. Exploratory laparotomy revealed a placental site trophoblastic tumor in the uterus. Wedge biopsies of the ovaries showed extensive luteinization of the ovarian stroma in both ovaries. Concentrations of testosterone, dihydrotestosterone, and androstenedione were markedly increased in the ovarian vein serum, indicating ovaries as the source of these steroids. The serum concentration of hCG was 69 mIU/mL. Pulsatile secretion of LH persisted in spite of elevated hCG levels. Follicle-stimulating hormone levels were low or undetectable. Elevated hCG levels and low FSH levels resulted in a hormonal environment similar to that seen in polycystic ovary disease (high LH to FSH ratio), resulting in extensive stromal luteinization. Decline in hCG levels after removal of the tumor resulted in the return of androgen levels to normal. 