1 d n ideal conditions, with selected patients, skilled doctors and ltramodern equipment. Effectiveness is its utility in real-life ituations, where patients are not selected, doctors are not ecessarily super-skilled and the equipment is not always the atest. Efficiency refers to each individual patient’s gain. In other words, efficacy answers the question whether the easure works; effectiveness, whether it really works in all ituations; and efficiency, whether it works for the patient we re dealing with [1]. Colonoscopy is no exception to this rule and has to be ssessed from the point of view of effectiveness more than fficacy alone. The ideal would be to investigate its effect n patients’ health when extended to use in all possible sitations, but obviously this is not easy—probably impossible n fact. An analysis of the clinical charts of more than 2000 lish the risk class (according to ASA) with a 100% threshold, concomitant anticoagulant treatment, and the need for antibiotic prophylaxis. The third group, insertion, reminds us that the rate of caecal intubation should not be less than 90% of cases—95% for screening—and that the landmark used to identify the end of the caecum should be recorded (best photographed) in all cases. The fourth, colonoscope withdrawal, insists that the instrument should not be withdrawn in less than 6–10 min, and that the percentage of polyps observed should be recorded (mean > 25% for men older than 50 and >15% in women 50 or older). The fifth group (biopsy and polypectomy) comprises the number of biopsies needed for surveillance of IBD colitis (about 30); documentation of the size, shape and site of polyps; and the percentage of polyps removed and sent for ases of colorectal cancer identified in 20 hospitals in Indiana USA) [2], in 1997, found that colonoscopy was not infallible 97.3% sensitivity for the diagnosis of cancer in the hands of astroenterologists and 87% when done by non-specialists). histological examination (>95%). A sixth group (complications) states that no patient should undergo colonoscopy without first signing an informed consent form listing the main potential complications (respiratory insufficiency in l b s b