A plasma testosterone/androstenedione (T/A) ratio was calculated in 15 women with possible ovarian neoplasms and androgen excess and whose mean plasma concentration of testosterone approached or was greater than a twofold elevation. The T/A ratio approached unity in eight of nine patients with polycystic ovarian disease, whereas all patients with hyperthecosis and two of three patients with androgen-secreting tumors had a testosterone/androstenedione ratio above 1.5. In 13 of 16 patients with androgen-secreting tumors of the ovary reported in the literature, the testosterone/androstenedione ratio was above 1.5. An elevated testosterone/androstenedione ratio should raise the suspicion of either an ovarian androgen-secreting tumor or hyperthecosis.