Three immunochemically and electrophoretically distinct lipoproteins, LP-A, LP-B, and LP-X,(1) were isolated from the low density lipoprotein fraction (1.006-1.063 g/ml) in plasma from patients with biliary obstruction by a separation procedure which combines ultracentrifugation, heparin precipitation, and ethanol fractionation. This method, here described, permits the quantitative determinatio...