Acute and chronic intubations of ethanol to pregnant rats produced changes in spontaneous fetal behavior four hours later. Fetuses from mothers in intermediate alcohol groups (4 and 6 g/kg) were substantially less active than controls (0 g/kg), but fetuses from low (2 g/kg) and high (8 g/kg) alcohol groups showed little indication of behavioral suppression. Circulating levels of alcohol in maternal blood, fetal homogenate and amniotic fluid at the time fetuses were observed confirmed that fetuses were exposed to alcohol in utero, but the measured concentrations of alcohol were not predictive of fetal activity. We suggest that some of the developmental consequences of Fetal Alcohol Syndrome may be the consequence of fetal inactivity induced by alcohol in utero.