Apo E was purified from the very low density lipoprotein (VLDL) of normal and hypertriglyceridemic subjects by Sephadex G-75, heparin-Sepharose 4B affinity chromatography, and preparative SDS polyacrylamide gel electrophoresis. The antisera were produced by injecting apo E into goats. With apo E antisera, Rocket immuno-electrophoretic method was developed to quantitate apo E levels in normal and hypertriglyceridemic human serum. The detection limit was 5.5 ng apo E. The coefficients of variation of intra- and interassay were 2.6% and 5.2%, respectively. The serum apo E level of 50 normal lipodemic subjects in Chengdu area was 4.7 +/- 1.2 mg/dl.