In 15 patients (13 women and two men) with cholesterol stones in the gall-bladder a special (Thistle) catheter was introduced into the gall-bladder under local anaesthesia by percutaneous transhepatic puncture. Methyl-tert-butyl ether, 2-15 ml, was injected via the catheter and removed again after 2 min. The number of stones per gall-bladder averaged 6.3 (1-20), size of stones 1.7 cm (0.5-2.8 cm), and duration of treatment 11.9 h (5-24 h). The stones dissolved in 13 patients (87%). In three patients stone débris remained: in one it was ultimately sucked out after reduction of the amount of débris with an EDTA-containing solution. The side effects of treatment--nausea and vomiting--were minor. In one patient there was a leak of bile from the gall-bladder after the procedure; a cholecystectomy was uneventfully performed. Another patient developed haemobilia which responded to conservative treatment. MTBE treatment has thus proved to be a successful and cheap method, low in side effects, in the treatment of patients with gall-stones.