Gossypol, an antifertility ingredient of the cotton plant, altered specific activity of mouse liver alcohol dehydrogenase (L-ADH) and subcellular aldehyde dehydrogenase (L-ALDH) in mice of both sexes. 2. Intraperitoneal injection of a single gossypol dose, 50 mg/kg, inhibited both male and female L-ADH and cytoplasmic L-ALDH from saline controls 21 hr after drug treatment. 3. Gossypol inhibited female but not male mouse mitochondrial L-ALDH isoenzymes. 4. Gossypol-produced enzyme inhibition was determined as noncompetitive. 5. The results suggest gender-dependent sensitivity of mitochondrial L-ALDH to the gossypol inhibition. A toxic metabolic interaction between ethanol and gossypol has been indicated which suggests the contraindication of alcoholic beverages during gossypol use.