There are ongoing multicenter European trials analyzing, among other factors, technical aspects of colonoscopy in various countries. The aim of the study was to compare the techniques of preparation and performance of colonoscopy in the Department of Gastroenterology at Medical University of Silesia in Katowice and other gastroenterology centers throughout Europe. The trial was conducted between January 1st 2001 and May 30th 2001 in 18 centers in 9 European countries. 307 consecutive patients, who signed consent forms, were recruited in Katowice, while 5697 patients were enrolled in other centers. The data were collected in a dedicated sheet, prepared in the coordinating center in Lausanne (Switzerland). The part concerning methods of bowel preparation was filled in before colonoscopy and the remaining questions (sedation, number of persons involved, duration, completeness, diagnosis, complications) were answered after the procedure. The data from all centers were analyzed in Lausanne and the results were sent back to the participants. The comparison of results from Katowice and other centers was performed in Katowice. We found out, that the type of cleansing the gut did not influence the quality of bowel preparation. Colonoscopy was performed under deep sedation (in the presence of anesthesiologist and anesthesiology nurse) more frequently in Katowice than in other centers. Differences between Katowice and the rest of centers in the other technical aspects of colonoscopy were of minor importance.