Biological alcohol markers give the possibility of an objective detection of alcohol abuse, independent from informations on consumption. They are especially suited for screening, (early) diagnosis, and differential diagnosis and for monitoring of relapse after treatment. A short review presents diagnostic significance and value of different alcoholism markers. Conventional state markers as gamma-GT, GOT/GPT (resp. AST/ALT, Aspartat-Amino-Transferase/Alanin-Aminotransferase), MCV (mean corpuscular volume) and especially CDT (carbohydrate deficient transferrin) as a new marker reveal the highest practical relevance for the diagnosis of a surreptitious and chronic alcohol consumption resp. abuse. CDT is elevated after a daily alcohol consumption of at least 50-60 g over 2-3 weeks, gamma-GT rises are typical after 4-6 weeks and MCV after 2-3 months. Elevated levels of methanol as well as isopropanol are characteristic for long time phases of alcoholization resp, alcohol abuse. In general the diagnostic specificity and sensitivity is higher in alcoholics than in unselected populations. The combined evaluation of various parameters with different pathobiogenesis elevates specificity, sensitivity and diagnostic efficacy and enables estimations of different patterns of alcohol abuse. CDT has an unprecedented high specificity of at feast 90% and is especially suited for differential diagnosis of alcoholic and nonalcoholic diseases.