['To test the value of phosphatidylethanol (PEth) as a biomarker for alcohol consumption among injecting drug users (IDUs).', 'As part of a longitudinal study of young IDUs, dried blood spots and self-reported alcohol by structured interview were collected at baseline. We compared self-reported alcohol use to detectable PEth (≥8\u2003ng/ml) in the blood spots as well as the relationships between quantitative PEth results and quantity measures of alcohol consumption.', 'There were strong associations between PEth and self-reported categorical measures of alcohol consumption (all P < 0.01). There was high specificity for reporting abstaining from alcohol; 94% of those who reported not consuming alcohol in the prior month tested negative for PEth. PEth was well correlated with measures of alcohol use (e.g. with reported number of days drinking in the prior month: Spearman r = 0.70 (P < 0.001)).'] Does comparison of phosphatidylethanol result to self-reported alcohol consumption among young injection drug users?