The aim of the present study comparing patients with mild to moderate hypertension with controls, was to explore a possible association between hypertension-related target organ damage and evaluation found in the gene encoding apolipoprotein E (apo E) genotype. Detailed medical history was recorded and physical examination was per-formed for all patients in the study (88 hypertensives, 63 normotensive controls). PCR (Polymerase Chain Reaction), RFLP (Restriction Fragment Length Polymorphism), and agarose gel electrophoresis techniques were used to determine the apo E genotypes. The frequencies of apo epsilon2, apo epsilon3, and apo epsilon4 alleles were 3.97, 88.06, and 9.95%, respectively in the hypertensive group. The frequencies of apo epsilon2, apo epsilon3, and apo epsilon4 alleles were 5.5, 92.0, and 2.38%, respectively in the control group. There were about twice as many individuals in the heterozygote hypertensive group who had apo E3/4 as compared to the control group (7.30 vs. 2.38%) (p = 0.07). The hypertensive patients who were carriers of the apo epsilon4 had significantly higher organ damage (left ventricular hypertrophy (p < 0.001). dilated left atrium (p < 0.05), retinopathy (p < 0.05)) as compared to those who were not carriers of apo epsilon4. These results showed a trend for the epsilon4 allele to be associated with a higher prevalence of target organ damage in patients with mild to moderate hypertension. Copyright (C) 2001 John Wiley & Sons, Ltd.