The aim of this study was to evaluate the effect of a recently developed biphasic multicomponent solvent in 39 patients with biliary duct stones that are too large (15-35 mm) to be removed after endoscopic sphincterotomy. From November 1991 to October 1993, 37 patients with common bile duct stones were papillotomized during endoscopic retrograde cholangiography and a nasobiliary catheter was positioned above the stone. In 2 patients, the residual stones were dissolved via the T-tube inserted during cholecystectomy. Solvent mixtures (solvent 1:26 mM ethylene diamine tetraacetic acid, 40 mM sodium deoxycholate and 30% dimethyl sulfoxide in an aqueous buffer solution glycine-NaOH, pH: 9.2; solvent 2: a 70: 30 mixture of dimethyl sulfoxide and methyl-tert-butyl-ether) were infused continuously and alternatively for 2 h at a rate of 0.3-0.5 ml/kg b.w./h. In order to diminish the absorption of the solvent from the duodenum, charcoal was given orally periodically. Fluoroscopy indicated that the common bile duct stones disappeared during 13-24 h of infusion in 10 of 39 patients. In 25 patients, the size of the stones diminished sufficiently for them to be removed by basket extraction. In 4 patients, the size of the stone did not change and surgery (1 pt) or endoscopic stenting (3 pts) was required. Only mild toxic side-effects were observed, including laboratory abnormalities and moderate duodenitis (34/39). Transient abdominal pain and/or cramp (21/39), nausea and vomiting (34/39) and diarrhoea (19/39) were the most common complaints during treatment.(ABSTRACT TRUNCATED AT 250 WORDS)