The ability of exogenous estrogens to alter serum levels of gonadotropins in ovariectomized rhesus monkeys was investigated in an attempt to develop a nonhuman primate model that could accurately predict both effective levels and physiologic consequences of human estrogen exposure. The ability of zearalenone (Z) and diethylstilbestrol (DES) to induce either a depression or an elevation of luteinizing hormone (LH) or follicle‐stimulating hormone (FSH) concentrations was compared to that of estradiol‐17β (E2). E2administration initially caused a reduction of gonadotropin levels (3–15 hr after injection) followed by an LH but not always an FSH surge (36–72 hr after injection). Injection of DES and Z induced similar gonadotropin patterns. The ovariectomized rhesus monkey model was used to compare the oral and parenteral potencies of Z, DES, and E2. The minimal doses of Z, DES, and E2that depressed LH levels after subcutaneous injection were 14, 0.5, and 4 μg/kg, respectively. When given orally, doses of 400, 2.5, and 5 μg/kg of Z, DES, and E2were needed to induce a significant decline in LH concentrations. FSH levels were depressed by injection of 56, 2, and 1 μg/kg of Z, DES, and E2, respectively. Additional experiments were conducted to determine whether DES or Z would interfere with either the E2‐induced gonadotropin depression or the subsequent gonadotropin peak. Since progesterone has been shown to block the estrogen‐induced LH surge but not to affect the LH depression, it was included as a positive control. As expected, progesterone blocked the induction of LH peaks by estradiol benzoate injection (40 μg/kg). Neither Z nor DES affected the LH peak or the depression.