Male rats fed with 30 mg/kg gossypol for 2 or 4 weeks exhibited a decrease in growth but showed no change from control in serum potassium levels. Serum aldosterone levels remained unchanged, but serum testosterone levels were significantly reduced after 4 weeks of treatment. Serum T3 was significantly increased after 2 or 4 weeks of treatment, while serum T4 was not different from control. It is concluded that gossypol at a dose that is sufficient to produce sterility in rats did not change serum potassium and aldosterone levels.