This document presents a comprehensive overview of biochemistry and physiology of transferrin (Tf) and carbohydrate-deficient transferrin (CDT) and on the role of CDT as alcohol abuse marker. It discusses the characteristics of the available analytical methodologies for CDT determination and finally presents a set of recommendations. CDT measurements should be performed only in accredited laboratories, having a quality system in place and regularly performing IQC and participating in EQAS. Unequivocal patient identification and a documented chain of custody are needed. Non hemolysed serum is the preferred sample and, if it has to be stored for more than 8 h, freezing at -20°C is recommended. Immunological methods are acceptable only as first level testing. A confirmation of positive findings with analytical methods based on different physicochemical principles is recommended. The result should be expressed as percentage of disialo-Tf on total Tf. Each laboratory should establish its own decision limit based on the characteristics of the analytical method used and on the scope for which the measurement is performed. The employed analytical method should be indicated in the final report.