The identification of the fetal alcohol syndrome in man has led to an abundant, but sometimes contradictory body of research examining the effects of prenatal ethanol exposure in animals. The present study examines the early sensorimotor development of heterogenous stock mice after ethanol exposure during one of two time periods in gestation, days 8--12, or days 14--18. Animals received either a liquid diet containing 20% ethanol derived calories, an isocalorically balanced yoked control diet or a lab chow control diet. Results indicated no apparent effects due to administration of alcohol during the middle of gestation, but a marked decrease in offspring viability, birthweight, and growth due to administration during the last part of gestation. The late gestation treatment group also showed a slight delay in the rate of development of the grasping and horizontal screen tasks. Overall, animals that survived showed relatively normal sensorimotor development.