Introduction: Flexible sigmoidoscopy (FS) has been shown to offer a substantial reduction in the mortality rate from colorectal cancer (CRC) located in the distal colon and is included in the CRC screening program in the UK and other countries. Although quality performance indicators for colonoscopies have been widely adopted, similar practice for FS is variable. For FS to become an effective screening tool for CRC, standardization of quality assurance is needed. Methods:We performed a retrospective study using an electronic endoscopy database to evaluate the practice of FS in terms of performance indicator during 2009-2011 in three district general hospitals in the UK. The patient's age, sex, extent of examination, grade of endoscopist, use of medications, type of bowel preparation, procedure tolerance, bowel visualization and missed left sided lesions were investigated.Results: A total of 3823 procedures were recorded, of which 87.5% were carried out in the outpatient setting. In 56.7% of cases, the colon was intubated to the splenic flexure or beyond, while examination was limited to the descending colon in 20.2% of cases, sigmoid colon in 18.7% of cases and rectum in 4.6% of cases. Procedure failure was caused by poor bowel preparation in 3.7% of the cases, pain in 1.5% of the cases and anatomical complexities and pathology encounter in 1% of the cases, while in 94.1%, there were no limitations. Good mucosal visualization was achieved in 76.1% of the cases, while the procedure was well tolerated in 80.7% of the cases. 2% of the patients used Entonox and 3.3% received midazolam (range 1-5 mg, median dose=3 mg). Pathologies were detected in 50% of the cases while the procedure was reported as normal in 37% of cases and reported inconclusive in the remaining 13%. 11 patients (0.29%) had a subsequent diagnosis of a left sided malignant lesion within the segment of the colon examined during FS. Conclusion:This study identified a wide variability in the practice of FS in local UK hospitals and highlighted the lack of quality standards. It showed that FS is a widely practiced and useful diagnostic tool. However in order to make it a more effective screening tool for colorectal cancer, a standardization process for quality assurance is needed.