In this study, the authors developed a disease-specific health related quality-of-life (HRQOL) measure that differentiated patients with ulcerative colitis (with and without surgery) from patients with Crohn's disease (with and without surgery). The purpose of the measure, which was facilitated by a questionnaire, was to produce a patient-orientated HRQOL index applicable to physicians' day-to-day management, and to provide a quality assurance mechanism to assess outcomes for these chronic diseases. The interview-directed questionnaire contained 47 items covering the following 4 domains: functional/economic, social/recreational, affect/life, and medical/symptoms. The items were selected by the authors from clinical experience and literature review, and showed good test-retest reliability over a 2-week period. The questionnaire had construct validity based on those items that correlated with the Sickness Impact Profile (SIP), a standardised generic health profile measure. From the 47 questions, a quality-of-life index was constructed by condensing the questionnaire to include only those 18 items that significantly differentiated between the 4 patient groups. Using this questionnaire, the authors studied 164 ambulatory patients (94 with ulcerative colitis, 70 with Crohn's disease) from a registry developed at the Cleveland Clinic. All patients had had their illness for at least 10 years, and 62% had undergone surgery because of it. When comparing the groups, the authors found that patients with ulcerative colitis had a better quality of life than those with Crohn's disease. In addition, patients who had not had surgery for their disease had a better quality of life than those who had.(ABSTRACT TRUNCATED AT 250 WORDS)