The purpose of the present study was to examine the effect of the prostaglandin synthetase inhibitor ibuprofen (IBU) on the teratogenic actions of alcohol. On day 10 of pregnancy, C57BL/6J mice were injected subcutaneously with 25 mg/kg IBU or vehicle control. One hour later, the mice were intubated with 5.8 g/kg alcohol or an isocaloric control solution. A group injected subcutaneously with 150 mg/kg aspirin, followed by 5.8 g/kg alcohol 1 hr later, served as a positive control. The results showed that maternal alcohol treatment resulted in significantly decreased fetal weight and an increased number of fetuses with limb and kidney defects. Implantation sites and prenatal mortality were not affected. IBU did not have any effect on these dependent variables. IBU statistically antagonized the teratogenic effects of alcohol on fetal weight and dysmorphology. These effects, however, were not as marked as in the Aspirin-Alcohol positive control group. These results are discussed in the context of clarifying the role of prostaglandins in the etiology of alcohol-induced birth defects.