Transient hypertriglycericlemia occurs in patients with severe thermal injury, and some patients have a low learance of exogenous triglyceride (TG) from plasma. This suggests an impaired lipolysis. In the current study, we measured the levels of apolipoproteins required for clearance of endogenous and/or exogenous TG. Twenty-five thermal injury patients (18 men and 7 women) having an average of 52% ± 6% (SE) total burn surface area were followed for a period of nine weeks. The levels of plasma lipids and apolipoproteins C-II, C-III, E, and A-I were measured after a 12-hour “fast,” ie, prior to the parenteral administration of fat emulsion. The levels of plasma cholesterol and apolipoproteins C-II, C-III, and A-I were low. Plasma TG levels, however, were not abnormally elevated, while apo E levels were within normal range. The results indicate that therm-ally injured patients have reduced levels of apoproteins necessary for TG metabolism. This condition may predispose to intolerance of exogenous TG.