The TaqIA1 allele of the dopamine receptor gene D2 (DRD2) has been associated with alcoholism, as well as with other addictive behaviours. The exact nature of how the presence of this allele can be a vulnerability factor in the development of alcoholism remains unclear. In this study we found that the presence in the DRD2 genotype of the TaqIA1 allele in Spanish alcoholics is associated with higher levels of urine homovanillic acid (HVA) when compared to patients homozygous for the TaqIA2 allele. A sample of 142 Spanish male alcoholic patients was split into 2 groups on the basis of the presence or absence of the A1 allele in their genotype. The urine sample was analyzed by high performance liquid cromatography (HPLC), and the concentration of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and vanilylmandelic acid (VMA) was determined. We found a statistical difference in the concentration of HVA between the groups, that suggests this polymorphism could be related to the variance of urine HVA levels.