Polymorphic variants of A1A2B0 and MNSs systems were analysed in a sample of 300 alcoholic patients subdivided according to gender and family history of alcoholism. There was agreement between observed and expected frequencies assuming genetic equilibrium. No association between phenotypes or genes of the A1A2B0 polymorphism and alcoholism was found when the Woolf method was used to evaluate possible associations. In the MNSs polymorphism, when the Woolf method was applied, significant values of chi 2 suggest a possible association between alcoholism and this blood marker, but after Bonferroni correction this association was rejected.