AIM: To evaluate if the guidelines for the appro-priateness of performing colonoscopy by American Society for Gastrointestinal Endoscopy (AGSE) and Italian Society of Digestive Endoscopy (SIED) yield a good diagnostic efficacy and do not present risks of missing important colonic pathologies in an Italian population sample.METHODS: A total of 1017 consecutive patients (560 men and 457 women; mean age 64.4 ± 16 years) referred to an open-access endoscopy unit for colonoscopy from July 2004 to May 2006 were evaluated according to ASGE and SIED guidelines for appropriateness of performing the procedure. Diagnostic yield was defined as the percentage of relevant colonic pathologies of the total number of colonoscopies performed.RESULTS: About 85.2% patients underwent colono-scopy that was considered appropriate based on at least one ASGE or SIED criterion, while it was considered inappropriate for 14.8% of patients. The diagnostic yield of colonoscopy was significantly higher for appropriate colonoscopies (26.94% vs 10.6%, P < 0.001) than for inappropriate colonoscopies (5.3%). There was no missed colorectal cancer following the ASGE/SIED criteria.CONCLUSION: ASGE/SIED guidelines have shown a good diagnostic yield and the rate of missing relevant colonic pathologies seems very low. Unfortunately, the percentage of inappropriate referrals for colonoscopy in an open-access endoscopy system is still high, despite the number of papers published on the issue and the definition of international guidelines. Further steps are required to update and standardize the guidelines to increase their diffusion and to promote educational programs for general practitioners. AIM: To evaluate if the guidelines for the appro-priateness of performing colonoscopy by American Society for Gastrointestinal Endoscopy (AGSE) and Italian Society of Digestive Endoscopy (SIED) yield a good diagnostic efficacy and do not present risks of missing important colonic pathologies in an Italian population sample. METHODS: A total of 1017 consecutive patients (560 men and 457 women; mean age 64.4 ± 16 years) referred to an open-access endoscopy unit for colonoscopy from July 2004 to May 2006 were evaluated according to ASGE and SIED guidelines for appropriateness of performing the procedure. Diagnostic yield was defined as the percentage of relevant colonic pathologies of the total number of colonoscopies performed .RESULTS: About 85.2% patients underwent colono-scopy that was considered appropriate based on at least one ASGE or SIED criterion, while it was considered inappropriate for 14.8% of patients. The diagnostic yield of colonoscopy was significantly higher for appropri there was no missed colorectal cancer following the ASGE / SIED criteria. CONCLUSION: ASGE / SIED guidelines have shown a good diagnostic yield and the rate (26.94% vs 10.6%, P <0.001) for for inappropriate colonoscopies Of missing relevant colonic pathologies seems very low. Unfortunately, the percentage of inappropriate referrals for colonoscopy in an open-access endoscopy system is still high, despite the number of papers published on the issue and the definition of international guidelines. Further steps are required to update and standardize the guidelines to increase their diffusion and to promote educational programs for general practitioners.