Analyses of 12 population samples have revealed that the total serum cholesterol level is significantly higher in Lp(a +) than in Lp(a -) individuals. The difference is more pronounced in middle-aged and other people than in young persons, and the difference between Lp(a +) and Lp(a -) individuals is larger when LDL cholesterol rather than total serum cholesterol is considered. Lp(a -) individuals have a significantly higher triglyceride level than Lp(a +) individuals. The Lp(a) variation is genetically controlled. Thus, the present study has revealed a small but significant effect of a single, autosomal locus on lipids implicated in atherosclerosis. An association between the phenotype Lp(a +) and coronary heart disease has been demonstrated previously.