The effect of prenatal exposure to alcohol on the development of thermoregulation and behavioral thermogenesis was assessed in rats. Pups at 5, 10, 15, and 20 days of age were chosen from litters with one of three prenatal treatment histories: liquid diet with 35% ethanol-derived-calories (35% EDC), pair-fed control (0% EDC), or lab chow control (LC). Subjects were removed from the home nest and had their initial rectal temperatures recorded before placement alone in the center of an observational chamber in a testing room maintained at 23-24 degrees C. Rectal temperatures were recorded again every hour for the next 4 h. Speed to reach the wall for behavioral thermogenesis (wall-huddling) was also measured at each hourly interval. With increasing age, all pups displayed increasing ability to maintain their initial core temperature, but prenatal exposure to alcohol had a significant effect in retarding the development of thermoregulation. At 5 and 10 days of age, alcohol-exposed pups had significantly lower rectal temperatures at 1-4 h out of the nest compared to control pups. In addition, the speed to reach the wall was slower in 35% EDC pups than in pups from the two control groups, suggesting a deficit in behavioral thermogenesis as well. These results agree with others demonstrating alcohol-induced development delays, and may have implications for other behavioral deficits seen after prenatal exposure to alcohol.