AIM:To compare the results from computed tomography (CT) colonography with conventional colonoscopy in symptomatic patients referred for colonoscopy. METHODS: The study included 227 adult outpatients, mean age 60 years, with appropriate indications for colonoscopy. CT colonography and colonoscopy were performed on the same day in a metropolitan teaching hospital. Colonoscopists were initially blinded to the results of CT colonography but there was segmental unblinding during the procedure. The primary outcome measures were the sensitivity and specificity of CT colonography for the identification of polyps seen at colonoscopy (i.e. analysis by polyp). Secondary outcome measures included an analysis by patient, extracolonic findings at CT colonography, adverse events with both procedures and patient acceptance and preference. RESULTS: Twenty-five patients (11%) were excluded from the analysis because of incomplete colonoscopy or poor bowel preparation that affected either CT colonography, colonoscopy or both procedures. Polyps and masses (usually cancers) were detected at colonoscopy and CT colonography in 35% and 42% of patients, respectively. Of nine patients with a finaldiagnosis of cancer, eight (89%) were identified by CT colonography as masses (5) or polyps (3). For polyps analyzed according to polyp, the overall sensitivity of CT colonography was 50% (95% CI, 39%-61%) but this increased to 71% (95% CI, 52%-85%) for polyps ≥ 6 mm in size. Similarly, specificity for all polyps was 48% (95% CI, 39%-58%) increasing to 67% (95% CI, 56%-76%) for polyps ≥ 6 mm. Adverse events were uncommon but included one colonic perforation at colonoscopy. Patient acceptance was high for both procedures but preference favoured CT colonography. CONCLUSION: Although CT colonography was more sensitive in this study than in some previous studies, the procedure is not yet sensitive enough for widespread application in symptomatic patients. METHODS: The study included 227 adult outpatients, mean age 60 years, with appropriate indications for colonoscopy. CT colonography and colonoscopy were performed on the same day in a metropolitan teaching hospital. Colonoscopists were initially blinded to the results of CT colonography but there was segmental unblinding during the procedure. The primary outcome measures were the sensitivity and specificity of CT colonography for the identification of polyps seen at colonoscopy (ie analysis by polyp). Secondary outcome measures included an analysis by patient, extracolonic findings at CT colonography, adverse events with patient and patient acceptance and preference. RESULTS: Twenty-five patients (11%) were excluded from the analysis because of incomplete colonoscopy or poor bowel preparation that affected either CT colonography , nine patients (42% of patients, respectively. Of nine patients with a final diagnosis of cancer, eight (89%) were confirmed by CT colonography For polyps analyzed according to polyp, the overall sensitivity of CT colonography was 50% (95% CI, 39% -61%) but this increased to 71% (95% CI, 52 (95% CI, 56% -76%) for polyps (% ≥ 6 mm. Adverse events were uncommon but included one colonic perforation at colonoscopy. CONCLUSION: Although CT colonography was more sensitive in this study than in some previous studies, the procedure is not yet sensitive enough for widespread application in symptomatic patients.