The effects of protein malnutrition on haematological and serum biochemical values were evaluated in gossypol-treated rats which were simultaneously fed with ethanol. Gossypol caused anaemia, leucopenia and thrombocytopenia in malnourished animals, suggesting a depression of bone marrow activity. Gossypol also caused a significant elevation of serum alkaline phosphatase and alanine aminotransferase activities and increases in the concentrations of Mg++ and Ca++ with reduced albumin, regardless of the nutritional status. These changes were more severe with malnutrition. Ethanol alone caused a thrombocytopenia but no other significant haematological changes. However, it appeared to cause derangement of lipid and protein metabolism as reflected in serum cholesterol and urea. The toxic effects seen in gossypol-treated rats were significantly reduced in animals simultaneously given ethanol. As the livers of gossypol-treated rats were significantly heavier than in these animals, it seems possible that ethanol consumption enhances the ability of the liver to metabolize gossypol, thereby reducing its accumulation and consequently its toxicity. However, further studies are needed to determine the mechanisms responsible.