The effects of gossypol acetic on pregnancy, embryofoetal development and on some selected parameters of immunological response in mice were studied. Daily intragastric administration of gossypol (50 or 75 mg/kg/day) during day 1-15 of gestation in mice produced a dose-dependent embryocidal effect (37.8% and 94.5% respectively) of non-viable foetuses. There was a significant reduction in foetal bodyweight when pregnant mice were treated with gossypol, although no foetal abnormalities were observed. Lymphocyte transformation induced by mitogen concanavalin A, was not inhibited by pretreatment with gossypol (25, 50 or 75 mg/kg/day) for 10 weeks. However, both plaque-forming cells to sheep red blood cell immunisation and the total spleen cell population were significantly depressed by higher doses (50 or 75 mg/kg/day) of gossypol. The results of the present study indicate that gossypol is not teratogenic, but exerts embryocidal and a selective depression on humoral immune response at high dose levels (50 or 75 mg/kg/day). It is not clear, whether the dose-dependent embryocidal and/or immunodepressive effects of gossypol are mediated by the parent compound or its metabolites, or whether these findings have any clinical relevance.