Background: The Alcopatch is an improved transdermal dosimeter for the measurement of alcohol consumption, by detection of ethanol in fluid excreted from the skin. The device is worn as a band around the ankle and provides a visual signal in the event of tampering. Methods: Fourteen volunteers wore duplicate Alcopatches for a period of 7 or 8 days, while keeping a written record of their beverage alcohol consumption. Ethanol concentration in the Alcopatch was measured by gas chromatography and correlated with self-reported consumption. Results: All alcohol consumption in excess of 0.25 g/kg/day resulted in measurable levels of ethanol in the Alcopatch. A positive correlation was observed between the reported consumption of ethanol (in g/kg/day) and the concentration of ethanol in the Alcopatch (square root, in mg/dl) (y= 0.91x + 0.28, r= 0.61) in 12 of 14 subjects. Conclusions: The Alcopatch detected the consumption of beverage alcohol with high sensitivity and specificity over a period of 7 to 8 days and may be useful for the study of target populations.