It is shown that phenotypic correlation of atherogenic index (AI)-[(total cholesterol--HDL-cholesterol)/HDL-cholesterol] with liability to IHD equals to 0.47. Based on AI values, the discrimination of individuals into the groups with IHD and without it could be obtained with the error of 29%. Intrapair correlations in the groups of twins and offspring-parent are as follows: rmz = 0.669 (125 pairs), rdz = 0.342 (228 pairs), rop = 0.466 (65 pairs). Partition of AI total phenotypic variance based on correlations among relatives by the least square method allowed to obtain the following estimates: Ga = 68.5%, Ew = 31.5%. Based on the monogenic model, inheritance of "hyper-AI" phenotype (AI higher than the 90% threshold of normal distribution) corresponds to the quasidominant mode with the parameters: p = 12.8% (frequency of the "hyper-AI" allele), II2 = 78.8% (penetrance of homozygotes for the tested allele), II1 = 39.4% (penetrance of heterozygotes) provided that penetrance of opposite homozygotes II0 = 0.