Abstract : Nowadays the influence of polymorphism of the ET-1 gene on the plasma levels of this peptide in patients with essential hypertension and congestive heart failure is poorly understood. 191 men were examined: 79 from the control group, 62 with uncomplicated essential hypertension and left ventricular hypertrophy, and 50 men with essential hypertension and congestive heart failure IInd-IIIrd classes. All patients were between the age of 40-60 years, and were residents of the Podillya region in Ukraine. Lys198Lys genotype and the Lys allele of the ET-1 gene dominate among residents of Podillia region in Ukraine. In patients with essential hypertension the level of ET-1 was significantly higher than that of the control group, with the highest concentration of peptide in individuals with congestive heart failure IInd-IIIrd classes. In men carriers of Lys198Lys genotype, the plasma concentration of ET-1 was significantly lower than in carriers of the Asn allele. In carriers of genotype Lys198Lys the highest level of peptide in plasma was determined in patients with congestive heart failure IInd-IIIrd classes. Men with uncomplicated essential hypertension with left ventricular hypertrophy, carriers of Lys198Lys genotype were more likely to encounter 2nd degree hypertension and carriers of Asn allele – 3rd degree hypertension respectively. In patients with congestive heart failure IInd-IIIrd classes, carrier of the Asn allele was seen to be associated with 3rd degree hypertension.