Alcohol consumption by young actively growing rats has been previously demonstrated to decrease bone density. This study addresses the mechanism of alcohol action on the early phases of bone growth and development using histomorphometric techniques. Four-week-old, female Sprague-Dawley rats were divided into three groups. Alcohol-treated animals were fed a modified Lieber-DeCarli diet ad libitum containing 35% ethanol-derived calories, whereas the pair-fed animals (weight-matched to ethanol rats) received an isocaloric liquid diet in which maltose-dextrin-substituted calories were supplied by ethanol. Chow animals were fed a standard rat chow ad libitum. Proximal tibiae, including epiphyseal growth plate, were removed for analysis after 2,4, 6, or 8 weeks on the diets. Trabecular volume and number were greatly reduced in the alcohol-fed animals; however, bone formation rates and mineralization rates were normal. Epiphyseal growth rate and proliferation rate were essentially stopped in the alcohol-fed animals.