Egg lecithin was adsorbed significantly by cholesterol monohydrate crystals. Adsorption data obtained at initial concentrations of less than 1.1 mM lecithin fitted the Langmuir equation. The calculated adsorption capacity suggested formation of a lecithin bilayer or a mixed bilayer of lecithin and cholesterol. The amount of lecithin adsorbed was highly dependent on the cholate concentration in the incubation medium. Minimal adsorption was observed at approximately 5 mM cholate. The presence of quaternary ammonium slats and dioctyl sodium sulfosuccinate caused desorption. The finding of an adsorptive layer supported the existence of an interfacial barrier than controls cholesterol dissolution.