BACKGROUND: Conversion during laparoscopic cholecystectomy has adverse effects on operating time, postoperative morbidity and hospital costs. Identifying risk factors for conversion is thus important to help surgeons to plan and counsel the patient and arranging operating schedules accordingly. This study evaluated retrospectively preoperative and intraoperative risk factors for conversion in 906 laparoscopic cholecystectomies for gallbladder calculosis. METHODS: Examined preoperative variables were: age, sex, obesity, arterial hypertension, diabetes, previous acute myocardial infarction, chronic obstructive pulmonary disease, non-ischemic heart disease, chronic hepatitis, hepatic cirrhosis, previous pancreatitis, biliary colics, endoscopic retrograde cholangiopancreatography (ERCP) and abdominal or cardiac surgery, as well as pain, fever, a high white blood cell count, ultrasound signs of cholecystitis at hospitalization. Intraoperative variables were: adhesiolysis, associated hepatic biopsy. RESULTS: Twenty-five operations were converted (conversion rate: 2.76%). Factors significantly associated with conversion were: age over 60 years, diabetes, previous supramesocolic abdominal surgery, ultrasound signs of cholecystitis, white cell count over 9x103/dl, previous acute myocardial infarction and preoperative ERCP, intraoperative adhesiolysis (0.001 CONCLUSION: Systematic evaluation of these factors in patients scheduled for laparoscopic cholecystectomy may help predict difficulties of the procedure, allow patients to be better informed about possible conversion, and optimize the planning of interventions for cases at risk.