1. The effects of a single moderate dose of alcohol on blood pressure, heart rate and associated metabolic and endocrine changes were studied in 10 healthy subjects and compared with those of an isocaloric glucose control drink. 2. Systolic blood pressure rose at 1 h after both alcohol and the control drink. Therefore this early change was not specifically due to alcohol ingestion. Subsequently, there was a tendency (not statistically significant) for supine and erect systolic blood pressure to be reduced up to 8 h after alcohol ingestion. There were no consistent late changes in blood pressure observed over 7 days after alcohol. 3. Alcohol caused a marked tachycardia in both supine and erect postures which persisted beyond the time of detectable blood alcohol levels. 4. Blood sugar rose by a similar amount after alcohol and the isocaloric glucose control drink, but peak plasma insulin levels were higher after the control drink. 5. Plasma sodium rose in keeping with alcohol induced water diuresis. No significant changes in plasma potassium or magnesium were seen after alcohol. 6. Compared with the control drink there was no evidence from measurements of circulating adrenaline, noradrenaline, cortisol, aldosterone or renin of activation of the sympathoadrenal axis, adrenal cortex or renin-angiotensin systems after alcohol.