Plasma lipid, lipoprotein lipid, and low-density lipoprotein (LDL) apolipoprotein B (Apo B) levels were measured in 34 patients who had undergone heart transplantation and in two patients who had undergone heart-lung transplantation. In contrast to initial reports, atherogenic dyslipoproteinemias were common, with 14% of patients having increased LDL cholesterol levels, 16.7% increased triglyceride levels, 8.3% decreased high-density lipoprotein (HDL) cholesterol levels, and 22.2% increased LDL Apo B levels. Of interest, 14% of patients had an HDL cholesterol level greater than the 95th percentile of the general population. In four patients coronary arteriosclerosis developed after transplantation. All had an atherogenic dyslipoproteinemia. One had type II hypercholesterolemia, and one had isolated low HDL cholesterol levels. Two had hyperapobetalipoproteinemia, one of whom also had low HDL cholesterol levels. The results establish that atherogenic dyslipoproteinemias are frequent in patients after heart transplantation and suggest that these dyslipoproteinemias, along with rejection, may play a role in the pathogenesis of arteriosclerosis after transplantation.