A new dyslipoproteinemic state, characterized by two populations of very low density lipoprotein particles giving the electrophoretic appearance of two pre-beta bands, the double pre-beta lipoproteinemia, is described. Based upon the lipid and apoprotein composition, it can be inferred that the slow moving pre-beta component is probably made up of remnant very low density lipoprotein particles; the absence of apo B 48 in the very low density lipoprotein fraction in these subjects rules out the intestinal origin of this remnant. Clinical interest in the double pre-beta lipoproteinemia relates to its potential atherogenicity; in fact it seems to be causally associated with such pathological conditions as hypothyroidism, uremia and dialysis, which are frequently accompanied by clinical complications of atherosclerosis. Double pre-beta lipoproteinemia also shows familial aggregation. Six years follow-up in a large family kindred has demonstrated that the family members carrying the double pre-beta lipoproteinemia, develop an incidence of coronary and cerebrovascular events higher than that of family members without the double pre-beta lipoproteinemia.