Murine skin was thermally injured under controlled conditions in a standard high temperature burn model. After high-speed homogenization of the burned skin, a toxic fraction was isolated applying different purification procedures. It was demonstrated that high temperature burns produced chemical condensations and high molecular aggregates in the protein moiety of the skin. Plasma proteins were involved in these reactions. After the purification process, the high molecular aggregates were obtained not as pure proteins, but as lipid-protein micelles. In the lipid moiety itself, thermal decomposition products were detectable. The biological effects of the purified lipid-protein fraction were studied by aid of rat liver perfusions 5 days after intraperitoneal injection of the material measuring different biosynthetic activities of the isolated organ. Significantly reduced biosynthesis of urea and depressed gluconeogenesis were demonstrable. The biochemical results are paralleled by ultrastructural findings indicating that the lipid-protein complex from burned skin causes mitochondrial vacuolization in liver cells of treated animals.