AbstractMethyl‐tert‐butyl‐ether (MTBE), infused via a nasobiliary catheter, was used to treat 33 patients with bile duct stones in nine units around Britain. MTBE contributed to success in 12 (36 per cent) cases: seven passed stones spontaneously during MTBE infusion and five had partial stone dissolution allowing subsequent endoscopic extraction. MTBE was non‐contributory in 21 (64per cent) cases: four passed stones after MTBE was stopped, six were treated by subsequent endoscopic techniques without evidence of dissolution, seven underwent surgery, and four were treated conservatively (with one death). In at least ten of the 21 cases in which MTBE was non‐contributory, pigment stones were present. Forty‐two complications occurred in 26 (79per cent) patients. The efficacy of MTBE for treating bile duct stones might be improved by better methods of instillation and, since success may be related to technique, the use of MTBE should be restricted to units familiar with th