['Three-session days were introduced in our endoscopy unit to accommodate the increased demand resulting from the introduction of the National Health Service Bowel Cancer Screening Programme (BCSP). Cecal intubation rate (CIR) and adenoma detection rate (ADR) may decline with time during a standard working day, but data are lacking for an extended three-session day. We assessed colonoscopy performance in an extended three-session day.', 'Colonoscopies performed during the year 2011 were retrospectively analyzed. The CIR and ADR were analyzed according to the time of day when procedures were done: morning (AM), afternoon (PM), or evening (EVE). Because of an expected higher incidence of adenomas in the BCSP patients, ADR was analyzed according to indication (BCSP or non-BCSP).', 'Of the 2574 colonoscopies, 1328 (51.7\u200a%) were in male patients and 1239 (48.3\u200a%) in female patients with a median age of 63 years (interquartile range [IQR], 51\u200a-\u200a70). Of the 2574 colonoscopies, 1091 (42.4\u200a%) were performed in AM lists, 994 (38.6\u200a%) in PM lists, and 489 (19\u200a%) in EVE lists. Time of day did not affect the CIRs for the AM, PM, and EVE lists (90.5\u200a%, 90.1\u200a%, and 89.9\u200a%, respectively; χ (2) [2, N\u200a=\u200a2540]\u200a=\u200a0.15, P\u200a=\u200a0.927). The CIR was reduced in female patients and those with poor bowel preparation (P\u200a<\u200a0.05). After exclusion of the BCSP patients, the ADR was lower in the EVE lists than in the AM and PM lists on univariate analysis, but on multivariate analysis, this difference was not significant (P\u200a>\u200a0.05). The ADR was significantly higher in patients older than 60 years and in men (P\u200a<\u200a0.001). Queue position did not independently influence the CIR or ADR.'] Is colonoscopy performance stable during the course of an extended three-session working day?