Infant rat pups, fed through intragastric cannulas from postnatal day 4 through day 18, showed a 19 percent reduction in total brain weight when ethanol was included in their diet on days 4 through 7. This reduction in brain weight occurred even though body growth in the experimental rats was equal to that of their littermate controls. The ethanol-exposed animals were markedly hypoactive during the period of drug administration, then displayed gross body tremors for 3 to 5 days. Throughout the study, the animals treated with ethanol had poor motor coordination and were hyperresponsive. These brain and behavioral effects appear similar to those seen in fetal alcohol syndrome.