Drug therapy of cholelithiasis with chenodeoxycloic acid (CDC) will yield better results, if patients with new cholesterol stones are selected for therapy, since these stones dissolve quickly and completely. X-ray diagnosis of the different types of stones is discussed; radiolucent bilirubin stones with or without cholesterol covering and with low calcium content do present the most difficult diagnostic problems. Old cholesterol stones do not disolve completely. If litholysis is supposed to be succesful, the diameter of a solitary cholesterol stone should not be greater than 20 mm and the total volume of cholesterol stones should not occupy more than 50% of the gallbladder volume in order to allow sufficient contact of the stones with the bile. Litholysis may be stopped if calcium salts or pigments cover the surgace of the stone. At the present stage only 24% of all patients with gallstones are suited for CDC-therapy. Early diagnosis of cholelithiasis is essential, if CDC-therapy is to be applied more frequently and if this form of therapy is to have better effects.