Catechol-O-methyltransferase (COMT) inactivates neurotransmitters, catechol hormones and drugs such as levodopa and methyldopa. A low activity allele has been demonstrated at codon 108/158 of the soluble and membrane-bound COMT, respectively, whereby a G to A transition results in a valine to methionine substitution. Ethnic and inter-individual differences in red blood cell COMT activity have been observed in the different populations studied so far. Since, no information is available on inter-individual variability of COMT genotype in Turkish population, we genotyped 217 healthy, unrelated Turkish individuals. The allelic frequencies of COMT gene in the Turkish population were found to be the same as has been observed in Caucasians., but different from Orientals.