Lung weight, DNA, RNA, protein, and total body weight were analyzed in fetuses from 14 pregnant Sprague-Dawley rats fed a nutritionally complete liquid diet containing v/v 6% ethanol (ethanol group). Each ethanol rat was matched with an isocalorically pair-fed animal (control group) who received the same liquid diet with carbohydrate substituted for ethanol. The rats were killed on day 20 of gestation. The mean maternal blood ethanol concentration at 0700 h on day 20 was 170 +/- 22 (SE) mg/dl. Compared to controls, ethanol fetuses had reduced body weight (21%), lung dry weight (39%), lung wet weight/body weight ratio (10%), DNA (21%), RNA (25%), protein (28%), and protein/DNA ratio (8%) (p less than 0.05). The results indicate that prenatal ethanol exposure inhibits cellular growth in the fetal lung, resulting in hypoplastic lungs which have fewer and smaller cells. The effect on the lung appears to be greater than on the body as a whole. These hypoplastic lungs may be predisposed to the development of pulmonary disease and may explain observations of more frequent and severe lower respiratory infections in children with prenatal ethanol exposure.