Solubilization of cholesterol, its fatty acid esters and gallstones were undertaken employing nonionic, anionic and cationic surfactants. Cholesterol was effectively solubilized by all of these surfactants. Cationic surfactants were most effective. However, cholesteryl myristate was not solubilized at all. In the dissolution test of gallstones in surfactant solutions, cationic surfactant solutions were exceptionally effective in dissolving gallstones. These results suggest the possible existence of interaction between alkylammonium radical and cholesterol on micellar surface.