In this study, ethyl glucuronide (EtG), a specific metabolite of ethanol, was for the first time detected in sweat after alcohol consumption by human volunteers. Sweat was collected using a sweat patch (PharmChek). After collection, chemicals accumulated on the patch were extracted with water and extracts were purified by solid phase extraction. EtG was determined by gas chromatography with mass spectrometric detection in negative chemical ionization mode. In parallel, the amount of sodium deposited on the patch was determined by capillary electrophoresis and used as a correction factor to calculate the volume of sweat accumulated on the patch and, hence, the concentration of EtG in sweat. The EtG sweat concentration observed ranged from 1.7 to 103.0 microg/L for alcohol consumption from 38.0 to 154.6 g equivalent pure ethanol. No EtG was detected in subjects who did not consume alcohol. Our results demonstrate that after ethanol consumption, EtG is detectable in sweat collected using a sweat patch. The simultaneous determination of sodium allows the estimation of the volume of sweat accumulated on the patch and to calculate the concentration of EtG in sweat. This represents the first quantitative determination of a xenobiotic in sweat collected using a sweat patch. This study suggests that EtG determination in sweat could represent an interesting alternative to urine or serum analysis for the control of abstinence of patients included in treatment programs.