For quality control purposes, a computer based auditing system for colonoscopy has been developed in the Department of Colorectal Surgery, Singapore General Hospital, Singapore. The first year's experience was reviewed to determine both workload patterns and the individual operators' performances. Colonoscopic completion rates, both as raw data and cusum transformations, were used as indices of quality control. The mean colonoscopic completion rate for the Unit was 97.0% and, when temporal trends were analysed by cusum, all operators consistently met or exceeded the minimum target completion rate of 90%.