We have previously described a general pattern of homogeneity in genetic and cultural determinants of blood lipids and lipoproteins among the major origin groups in the Israeli population. This paper reports on these determinants of total plasma cholesterol (TC), triglyceride (TG), low- and high-density lipoprotein cholesterol (LDL-C, HDL-C), and of the HDL-C/TC ratio, estimated from the total sample of 4,000 families whose members were examined in the Jerusalem Lipid Research Clinic. Both genetic (h²) and cultural (c²) components of inheritance were significant for all lipid variables. Under the most parsimonious model genetic heritability (h²) ranges from 0.45 for LDL-C, 0.47 for HDL-C to 0.64 for HDL-C/TC ratio. Cultural heritability (c²) was 0.03 for LDL-C, 0.04 for TC, 0.05 for TG and 0.07 for HDL-C and HDL-C/TC ratio. Within this population, as in others, genetic factors appear to be the major determinants of lipid variation, suggesting relative homogeneity of environmental correlates of plasma lipids.