Ethylglucuronide (EtG) is a biomarker of ethanol consumption, and the authors propose an overview of its potential use in clinical or forensic cases. This metabolite presents a higher half-life and is therefore detectable longer than ethanol itself, and allows, in the case of late sampling, the research of acute alcohol abuse in the days prior to urine sampling. Routine testing for urinary EtG can be easily introduced in laboratories since an immunochemical kit is available. However, it is necessary to take into account the cut-off values in order to interpret the results. EtG can also be tested in hair and is a very useful biomarker of chronic alcohol abuse. A recent international consensus has established cut-off values for the interpretation of EtG concentrations in hair. However, hair testing is still limited to specific laboratories as it is not easily implemented in routine, due to a specific sample treatment and to the lack of immunochemical kits.