Tolerance to colonoscopy varies between populations and data from the South East Asian region is lacking. We aimed to determine tolerance and safety with to colonoscopy; conscious sedation and identify risk factors for complications in Malaysian adults. Consecutive outpatients undergoing colonoscopy were enrolled prospectively. A combination of pethidine and midazolam were used and tolerance to colonoscopy assessed three hours post-procedure using a validated scale. All patients were monitored for cardiorespiratory depression and risk factors for complications were identified. Two hundred and eight patients (mean age 57.2 +/- 14.8 years, 48% female) were enrolled. The population ethnicity consisted of 45 (21.63%) Malays, 101 (48.56%) Chinese and 56 (26.92%) Indians. Conscious sedation was achieved with 5.0 +/- 1.1 mg of midazolam and 43.3 +/- 14.0 mg of pethidine. Thirty (14.4%) patients tolerated the procedure poorly and independent predictors included female gender (OR 2.93, 95% CI = 1.22 to 7.01) and a prolonged duration of procedure (OR 2.85, 95% CI = 1.08 to 7.48). Hypotension occurred in 13 (6.25%) patients, with age > 65 years as the only risk factor (OR 13.17, 95% CI = 1.28 to 137.92). A prolonged duration was the main cause of hypoxia (OR 5.49, 95% CI = 1.54 to 19.49), which occurred in 6 (2.88%) patients. No major complications occurred during the study period. The current practice of conscious sedation is safe and tolerated well by most adults in our population. However, poor tolerance in a notable minority may have significant clinical implications.