Frequencies of alleles and genotypes of a polymorphic marker 4a/4b of eNOS gene and association of this marker with parameters of hemodynamics, signs of left ventricular hypertrophy and endothelial dysfunction were studied in 78 uzbek men aged 50.5+/-9.5 years with stage I-II essential hypertension. Allele 4b and genotype 4b/4b were found to be most frequent while genotypes 4a/4b and 4a/4a were associated with high degree of left ventricular hypertrophy, disturbances of 24-hour blood pressure profile and pronounced diastolic dysfunction. Three months of therapy with nebivolol exerted similar antihypertensive effect in all patients however only in patients with 4b/4b genotype it caused regression of left ventricular hypertrophy and normalization of endothelial vasoregulatory function.