Studies involving body fluid homeostasis were carried out in adult Long-Evans rats whose mothers received liquid diets containing 35% of the calories derived from ethanol between the 6th and the 20th day of gestation. Control rats were offspring of pair-fed dams given isocaloric liquid diets containing no ethanol. Plasma levels of arginine vasopressin (AVP), plasma osmolality, urine production and urine osmolality were determined in both the water-sated (WS) and water-deprived (WD) conditions. Fetal alcohol exposure (FAE) induced a seven-fold increase in plasma AVP levels in the WS condition. Water consumption was significantly greater in the FAE animals but plasma osmolality, urine osmolality, and urine production were within the normal range. In the control rats, 24 hours of WD produced the expected increase in plasma AVP, plasma and urine osmolality. The FAE rats, however, showed only an increase in plasma osmolality and no significant change in plasma AVP or urine osmolality with WD. These data suggest that fetal alcohol exposure causes a long-term disruption in the central mechanisms regulating vasopressin release and therefore fluid homeostatic responses.