Clinical observations indicate that there is an association between hyperinsulinemia and hyperandrogenism in women of reproductive age. The effects of insulin on ovarian steroidogenesis were studied in 4-day incubations of minced porcine theca. Insulin alone significantly stimulated dihydrotestosterone (DHT), testosterone (T) and androstenedione (Δ4A) accumulation in the media as compared to vehicle-treated controls. Insulin alone did not stimulate progesterone (P) accumulation. Insulin plus luteinizing hormone (LH) resulted in significantly greater accumulation of DHT, T and Δ4A than LH alone. Insulin plus LH did not stimulate P accumulation as compared to LH alone. Insulin, at high concentrations, may be a regulator of thecal androgen synthesis.