A laparoscopic cholecystectomy has been accepted as one of the methods of treatment for patients with gallbladder(GB) pathology. Occasionally some cases can be diagnosed as cancer of the gallbladder incidentally after a laparoscopic cholecystectomy. We did 855 laparoscopic cholecystectomies from September 1991 to July 1996 and found 9 GB cancer patients after the operation. Most of the patients with GB cancer have a poor prognosis, but recently there have been some reports with good prognoses in this group of patients. The incidence of incidental GB cancer in laparoscopically resected GB specimens was 1.1% (9/855). The age distribution was between 44 and 72 yrs. Among the 9 cancer patients, 6 patients were found to have a GB mass as a result of the preoperative ultrasound examination. Four patients had mucosa-confined cancer and did not undergo any further treatment. One patient had mucosa confined cancer with a residual tumor in the cystic duct resection margin and underwent segmental resection of the liver (IVa & V) and segmental resection of the common bile duct, including dissection of the pericholedochal lymph node. The other four patients had advanced GB cancer with subserosal invasion. One patient underwent segmental resection of the liver (IVa & V) and segmental resection of the common bile duct, including dissection of the pericholedochal lymph node, and the other patient received a pericholedochal lymph node dissection only. The follow-up period ranged from 39 months to 3 months. Only one patient, who had mucosa-confined cancer with cystic duct invasion, died from lung metastasis with local recurrence of the midclavicular trocar site at 16 months after the laparoscopic cholecystectomy, but the other 8 patients have been doing well until now. We recommend a habit of opening the gallbladder, examining the gross pathologic features, and performing a frozen-section examination in patients where GB cancer is suspected. During that procedure, a careful isolation technique (careful dissection and delivery of the specimen in vinyl bag is vital) for preventing tumor implantation.