Purified human VLDL (d= <1.006 g/mL) is labeled with DiI (1,1-dioctadecyl- 3,3,3,3-tetramethylindocarbocyanine perchlorate). It is ultrafiltered through a membrane and packaged aseptically under nitrogen. The product is provided in a solution with 154 mM NaCl, 5.6 mM Na2HPO4, 1.1 mM KH2PO4, and 0.34 mM EDTA, at pH 7.4.