Lipoprotein changes have been investigated in 16 patients with burn injury. Serum, urine, and blister fluid were examined for apoprotein content. In the group of patients with moderate burns serum High Density Lipoprotein (HDL) fell drastically, and Low Density Lipoprotein (LDL) decreased slightly, whilst Very Low Density Lipoprotein (VLDL) rose. In blister fluid there was a greater loss of HDL apoprotein than LDL apoprotein or apoprotein C, whilst in concentrated urine a small quantity of HDL apoprotein could be detected. The loss of HDL, which is necessary as an apoprotein C receptor in the conversion of VLDL → LDL, may lead to a block in the conversion of VLDL to LDL. This may in part contribute to the hypertriglyceridemia, hypocholesterolemia, and hypophospholipidemia noted after burn injury.