There are 7 different alcohol dehydrogenase (ADH; EC 1.1.1.1) isozymes in human: three belong to class-I: alpha, beta, and gamma, one to class-II: pi, one to class-III: chi, one to class-IV: ADH7 and one to class-V: ADH6. Members of the ADH7 family metabolize a wide variety of substrates, including ethanol, retinol, other aliphatic alcohols, hydroxysteroids, and lipid peroxidation products. ADH7 is the only ADH not expressed in liver, instead being expressed mainly in the upper gastrointestinal tract. Genome-wide studies have identified significant associations between single-nucleotide polymorphisms in ADH7 with alcoholism, drug dependence and cancer, but the causative variants have not been identified[1].