We have studied a number of solutions that have been claimed to dissolve human gallstones in order to determine the best solution for treating, by irrigation, stones retained in the biliary tree. It has been shown that heparin solutions are ineffective in dissolving or fragmenting gallstones and that the most effective bile-salt solution is a 200 mM deoxycholate solution. However, deoxycholate has a number of intestinal side-effects which prevent its clinical use. 200 mM sodium cholate is the next most effective bile-salt solution and its side-effects are prevented by simultaneous administration of cholestyramine. A combination of deoxycholate and cholate has been shown to be more effective than a cholate solution and due to the smaller concentration of deoxycholate may lack the side-effects of the 200 mM deoxycholate solution. These differences in dissolving capacity between the different bile salts are eliminated when lecithin is added to the solution, and this study has shown that a 200 mM taurocholate plus 100 mM lecithin solution is as effective in dissolving gallstones as a 100 mM deoxycholate plus 100 mM cholate solution. A careful clinical trial of both the combination of deoxycholate plus cholate and taurocholate plus lecithin solutions is indicated.