Plasma arginine vasopressin (AVP) levels are frequently increased in patients with congestive heart failure (CHF). Further, AVP does not respond normally to certain osmotic and nonosmotic manipulations in this condition. As a test of the central suppressibility of AVP in CHF, an oral ethanol challenge was given (0.7 ml/kg body weight) to 10 patients with CHF and 10 normal control subjects, and the response of AVP, osmolality, heart rate and blood pressure was measured over the next 2 hours. In the CHF group, AVP was 9.6 ± 3.9 pg/ml (± standard deviation) at control and remained unchanged throughout the protocol. In the normal group, AVP was 6.9 ± 2.9 pg/ml at control and declined significantly to 4.9 ± 2.0 pg/ml at 20 minutes (p < 0.05). Osmolality and blood ethanol changes were similar in the 2 groups, as were those in mean arterial pressure. The administration of ethanol therefore did not result in an acute decrease in plasma AVP in patients with CHF, but did so in normal subjects. Differences in the response of blood pressure and osmolality do not explain the abnormality; hence, a defect in the central control of AVP release may exist in CHF. This observation may have implications for the mechanisms involved in the generation or maintenance of elevated AVP levels in patients with this disease.