At present, an instrument for measuring the quality of life, specifically for patients with gastrointestinal disease, is not available. A new instrument for gastrointestinal disorders that is system-specific has been developed in three phases. In the first phase, questions were collated and then tested on 70 patients with gastrointestinal diseases and those that worked well were retained. In the second phase, the questions were modified and tested on 204 patients and the results verified by international experts. The instrument was also validated against other generic measures of quality of life. During the third phase, the instrument was validated with 168 normal individuals. Reproducibility was tested on 25 patients with stable gastrointestinal disease and responsiveness was tested on 194 patients undergoing laparoscopic cholecystectomy. The result is a bilingual (German and English) questionnaire containing 36 questions each with five response categories. The responses to questions are summed to give a numerical score. It is concluded that the Gastrointestinal Quality of Life Index (GIQLI) is ready to be used in clinical practice and research.