The safety and efficacy of methyl tert-butyl ether (MTBE) dissolution of cholesterol gallbladder stones were evaluated in 25 patients with increased risk for surgery. Two patients were treated twice. The MTBE was infused and aspirated manually through a percutaneous transhepatic catheter to the gallbladder. The placement of the catheter failed in three patients (11%). In 19 of 24 patients (79%) there was complete dissolution of stones after a mean treatment time of 12.2 h (range, 4.3-19.5 h). In five patients treatment was discontinued before complete dissolution owing to technical problems or side effects. Side effects were nausea, pain, vasovagal reaction, and fever. Fifteen patients were followed up for a mean of 15.7 months after dissolution. Stone recurrence was found in eight patients, five of whom suffered symptomatic relapse. We conclude that dissolution therapy with MTBE is a safe and adequate alternative to surgery in selected high-risk patients.