Studies in various ethnic groups have shown contradictory evidence on the association of the angiotensin converting enzyme (ACE) insertion/ deletion (I/D) polymorphism with essential hypertension. In addition, mistyping of the insertion allele in heterozygotes has been reported. We analyzed the ACE genotype of 98 hypertensive and 84 normotensive subjects of Greek origin. Genomic DNA was extracted from blood samples and amplified by polymerase chain reaction (PCR). PCR primers were flanking the polymorphic region in intron 16 of the ACE gene. To avoid mistyping of heterozygotes, samples with the DD genotype were also amplified with primers that detect only the insertion allele. The distribution of the DD, ID, and II ACE genotypes was 30, 45, and 23 in hypertensive patients and 29, 40, and 15 in normotensive subjects, respectively. The estimated frequency of the insertion allele was 0.45 in hypertensive and 0.42 in normotensive subjects. The difference was not statistically significant. The results indicate a lack of association between ACE I/D polymorphism and essential hypertension in this Greek population, suggesting that other genes must contribute to the pathogenesis of hypertension.