Functional alternations of noradrenergic and dopaminergic neurotransmission have been implicated in suicidal behavior. A tetranucleotide repeat polymorphism in the first intron of the tyrosine hydroxylase (TH) gene, encoding a rate-limiting enzyme for the synthesis of catecholamines, is reported to have the potential to control expression of the gene and to be associated with suicidal behavior in patients with adjustment disorders. To test the hypothesis that TH gene polymorphisms are involved in suicide through an alteration of TH function, this tetranucleotide repeat polymorphism and the other two SNPs that cause a change in amino acid sequence were examined in suicide victims who completed suicide and control subjects. No significant differences in genotype distribution or allele frequencies were found between the two groups in the three polymorphisms. These findings suggest that these functional polymorphisms are not involved in a biological susceptibility to suicide.