Some patients who undergo colonoscopy that appeared to have cleared the colorectum of neoplasia return within a short interval (1-3 yr) with colorectal cancer. Although several a priori mechanisms could account for this occurrence, wide variation in detection rates of adenomas and cancer at colonoscopy suggests that suboptimal colonoscopic technique is a significant contributor. Optimal technique with white-light colonoscopy involves taking adequate time for inspection during withdrawal (an average of at least 6 min in normal colons), interrogating the proximal sides of folds, flexures, and valves, clearing fluid and debris, and distending adequately. Some adjunctive techniques are directed toward exposing more colonic mucosa during colonoscopy. Wide-angle colonoscopy appears to improve efficiency but does not eliminate miss rates. Colonoscopy in retroflexion was unsuccessful in reducing miss rates in one study, whereas cap-fitted colonoscopy was successful in reducing miss rates in one small study. Techniques to improve detection of flat lesions include pancolonic chromoendoscopy (CE). In two randomized controlled trials, CE improved adenoma detection, but CE does not appear to provide substantially greater yields than those obtained by the more sensitive white-light colonoscopists. Narrow band imaging and autofluorescence are being assessed for improved detection of flat lesions. Adenoma detection rates are an important measure of the quality of colonoscopy and should be reported to endoscopists in quality improvement programs in colonoscopy.