Three groups of families with different initial levels of arterial pressure in proband children were examined. The relationship was established between the levels of arterial pressure in children and those in their relatives of the first degree of kinship. Based on intrafamilial correlations, the phenotypic dispersion of systolic and diastolic arterial pressure was analyzed. It has been shown that as compared to the genetic factors, the environmental factors play a greater role in arterial pressure variability.