Serum albumin binds 2-lysophosphatidylcholine (lysolecithin) to form a complex. Two molecules of lipid bind strongly to a molecule of albumin; an additional five molecules bind more weakly (Nakagawa and Nishida 1973). The fate of the complex in vivo is unclear. In vitro 2-lysophosphatidylcholine can be esterified with fatty acid to generate phosphatidylcholine. Such a process could replenish the phosphatidylcholine consumed by cholesterol esterification in HDL particles, but the extent to which it occurs in vivo is unclear (Nakagawa and Nishida 1973; Switzer and Eder 1965).