Low molecular weight heparin (LMWH) and standard heparin were given intravenously to six healthy subjects receiving a continuous infusion of Intralipid. After infusion, antifactor Xa, antithrombin II and coagulation activity (Normotest) were the same for both heparins. Activated partial thromboplastin time increased significantly, but the increase was much higher after standard heparin (+473%) than after LMWH (+48%). The increase in lipoprotein lipase activity was less pronounced after LMWH infusion. This resulted in a smaller decrease in Intralipid-triglyceride concentration and a smaller increase in both plasma FFA concentration and Intralipid fractional removal rate compared to standard heparin. This study shows that the plasma lipolytic potential of LMWH is weaker than that of standard heparin when given in doses with equipotent anticoagulation. LMWH may therefore be preferable to standard heparin as an antithrombotic agent in clinical situations where a high plasma lipolytic activity may be disadvantageous.