A method of pereparing a rediographic contrast medium containing liposomes is disclosed, comprising (a) dissolving a phospholipid and a sterol in a supercritical or subcritical carbon dioxide in the presence of a compound containing a hydroxyl group or a polyalkyleneoxide group, (b) adding thereto an aqueous solution containing an iodine compound to form micelles and (c) discharging the carbon dioxide to form liposomal vesicles enclosing the iodine compound.
