Among the different possible genes involved in the alcoholism etiology, the X-linked monoamine oxidase A gene is a good candidate. The aim of this study was to assess whether a functional VNTR polymorphism in the promoter region of the monoamine oxidase A gene is associated with alcoholism, comparing patients of both sexes. Ninety-three alcohol-dependent patients (51 males, 42 females) and 93 sex-matched normal controls were engaged. In the total sample, the genotype containing at least one three-repeat allele was significantly more frequent among alcohol-dependent patients than controls (P=0.01). However, when the two sexes were analyzed separately, the difference was statistically significant only for females. This is of particular interest as rates of alcoholism in Brazil are markedly lower in females. Our results suggest that this monoamine oxidase A polymorphism could play a role in susceptibility to alcoholism, which may differ across sexes.