Little is known concerning the usefulness and feasibility of quality assurance programs in gastrointestinal departments. The aim of this study was to identify the indicators of quality in colonoscopy, to check their use in clinical practice, and to identify their threshold values.A prospective study was performed in four endoscopic units. In the first phase, a questionnaire was used to identify the indicators that were considered important and easy to record; in the second phase, the selected items were prospectively recorded.Data from 603 colonoscopies were evaluated. The selected indicators were: rate of cecal intubation, rate of examinations with normal findings, rates of complications, appropriateness of indications, use of a washing machine for disinfection, duration of the disinfection procedure, rate of procedures repeated due to poor colon cleansing, rate of operative procedures, length of waiting time, rate of procedures performed for follow-up of known disease, experience of the operator, and rate of procedures performed with the patient under conscious sedation. A striking difference emerged between the technical standards at three centers, which were fairly good, and the standard at the fourth center, which was less satisfactory. The length of the waiting time was high in all centers, as well as the rate of examinations conducted with an inappropriate indication. The rate of procedures performed under conscious sedation varied widely between the centers.The study of the indicators of quality of colonoscopy is feasible and easy to perform in clinical practice, and can be useful for quality assurance programs.