Lipoprotein lipase (LPL) plays a key role in lipid metabo-lism. Molecular modeling of dimeric LPL was carried out usingINSIGHT IIbased upon the crystal structures of human, porcine, and horse pancreatic lipase. The dimeric model reveals a saddle-shaped structure and the key heparin-binding residues in the amino-terminal domain located on the top of this saddle.