•A method for analysis of ethyl sulfate (EtS) in wastewater was developed.•Levels of the alcohol biomarker EtS in wastewaters ranged from 5.5 to 32.5μg/L.•A sewage epidemiology approach was applied for alcohol consumption estimation.•The estimated per capita alcohol consumption in the Barcelona area was 18mL/day.•Levels of EtS and some illicit drugs were correlated. The increasing, generalized consumption of alcohol, especially among young people, generates great concern in our society due to its negative consequences on public health and safety. Besides the traditional, official methods employed for estimation of alcohol consumption, the monitoring of ethyl sulfate (EtS), a urinary biomarker of alcohol ingestion, in raw wastewater has been recently proposed as an additional tool to estimate alcohol use at community level through the so-called sewage epidemiology approach. In the presented study, a fast and reliable analytical method based on ion-pair liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been optimized and further applied to the analysis of EtS in seven 24h composite samples collected along one week at the inlet of a large sewage treatment plant (STP) located in the Barcelona area. EtS was measured in the entire set of analysed samples, with concentrations ranging from 5.5 to 33μg/L, which correspond to an absolute alcohol consumption of around 11,000 (Wednesday) to 25,000 (Sunday) kg/day. The average per capita absolute alcohol consumption calculated was 18mL/day/inhabitant. Moreover, the levels of EtS measured throughout the week showed high correlation with those of some recreational illicit drugs and metabolites, namely, cocaethylene (r2=0.9391, n=5), benzoylecgonine (r2=0.9252, n=7), ecstasy (r2=0.8950, n=7), amphetamine (r2=0.8707, n=7) and cocaine (r2=0.6425, n=7), measured in the same samples. This study confirms that the analysis of EtS in raw wastewater can be a useful tool for the estimation of alcohol consumption in an anonymous, fast and economic way, and indicates that consumption of alcohol and some illicit drugs occurs often together.