A new classification of patients with Mirizzi syndrome and cholecystobiliary fistula is presented. Type I lesions are those with external compression of the common bile duct. In type II lesions a cholecystobiliary fistula is present with erosion of less than one-third of the circumference of the bile duct. In type III lesions the fistula involves up to two-thirds of the duct circumference and in type IV lesions there is complete destruction of the bile duct. A total of 219 patients were identified with these lesions from 17,395 patients with benign biliary tract diseases undergoing surgery. The incidence of type I lesions was 11 per cent, type II 41 per cent, type III 44 per cent and type IV 4 per cent. The majority had obstructive jaundice. In type I lesions, cholecystectomy plus choledochostomy is effective. In type II lesions, suture of the fistula with absorbable material or choledochoplasty with the remnant of gallbladder can be performed. In type III lesions suture is not indicated and choledochoplasty is recommended. In type IV lesions, bilioenteric anastomosis is preferred. Operative mortality rate increases according to the severity of the lesion, as does postoperative morbidity. During cholecystectomy, partial resection is recommended in order to extract the stones, visualize the common bile duct and define the type and location of the fistula. T tubes should be placed distal to the fistula.