Allelic variation at the CYP2D6 gene has been suggested to be associated with CNS disorders, including Parkinson's disease and Lewy body dementia. In order to elucidate whether a relationship exists between CYP2D6 polymorphism and the risk of developing Alzheimer's disease (AD), CYP2D6 allele and genotype frequencies have been evaluated in 94 patients from Southern Italy (29 men and 65 women, aged 74+/-8 years) with AD, and in 350 healthy controls (204 men, 146 women, aged 33+/-9 years) from the same geographical region. Allele frequencies among AD patients were not significantly different from those in healthy controls. Subjects could be divided in four CYP2D6 genotype groups: 52 (56%) patients and 205 (59%) controls carried no mutated alleles (homozygous extensive metabolizers (EM)), 33 (35%) patients and 109 (31%) controls carried one mutated allele (heterozygous EM), while 4 (4%) patients and 11 (3%) controls were found to have two mutated alleles (poor metabolizers (PM)). Five (5%) patients and 25 (7%) controls carried extra copies of a functional gene (ultrarapid metabolizers (UM)). Our results indicate that CYP2D6 polymorphism is unlikely to represent a major risk factor in susceptibility to Alzheimer's disease.