Excessive alcohol consumption poses a wide variety of significant immediate and long-term health risks. Ethanol biomarkers have clinical utility for detection, diagnosis, and treatment of alcohol use disorders as well as for screening for fetal alcohol exposure. Indirect biomarkers are those that reflect the toxic effects of ethanol on organs, tissues, or body biochemistry, whereas direct biomarkers are products of ethanol metabolism. Liver enzymes, carbohydrate deficient transferrin and mean corpuscular volume are discussed as examples of indirect markers of alcohol use. Commentary on the direct ethanol markers includes the following: acetaldehyde adducts, ethyl glucuronide, ethyl sulfate, phosphatidylethanol and fatty acids ethyl esters.