Patients frequently arrive in the emergency department under the influence of alcohol after exposure to extreme conditions of heat or cold. While ethanol ingestion and ambient heat are recognized to have vasodilatory action, previous studies of their interactive effect are limited and guidelines for patient care are vague. Xenon-133 skin perfusion studies allow direct quantitative assessment of the net effect of multiple variables on skin vasculature. Using Xenon-133 to measure cutaneous blood flow in the lower extremity, we studied four groups of 12 healthy men at 20, 25, 30, and 35 C. Half of each group ingested 60 mL of 95% ethanol in fruit juice, while the other half received placebo only. Skin perfusion at baseline and 50 minutes after ingestion of ethanol were measured. Vasodilatation was observed at 25 and 30 C in subjects who had ingested ethanol. At 20 and 35 C vasoconstriction or vasodilation, respectively, occurred in all subjects with no additional influence of ethanol observed. The influence of heat or cold on skin blood flow appears to dominate over the influence of moderate amounts of ethanol at these temperature extremes. Specifically, in patients exposed to extreme temperatures while under the influence of ethanol, there is no benefit from the agent on cutaneous blood flow at or below 20 C, and there is no enhanced heat loss at 35 C or above.