OBJECTIVES: Relapsing polychondritis is a rare, multi-systemic and inflammatory condition of unknown origin. We currently lack a core set of measures to assess and follow damage in patients suffering from this condition. Our primary aim was to derive a disease-specific damage measuring tool for relapsing polychondritis, the Relapsing Polychondritis Damage Index (RPDAM). METHODS: We performed an international 4-round multicenter Delphi study during which experts were asked to rate the relevance of potential damage items for relapsing polychondritis (141 items were obtained from a literature review and 12 from expert suggestion), using a Likert Scale. The selection of items for each subsequent round was based on the median rating of each item. RESULTS: Twenty-four experts from 11 nationalities participated in round 1 and 22 in rounds 2, 3 and 4. From the initial 153 potential damage items, 44 items were selected during round 1, 30 items during round 2 and 16 during round 3. During round 4, we refined the index to a total of 17 items referring to ear nose and throat, eye, respiratory, cardiovascular and hematological systems as well as to treatment-related specific damage items. CONCLUSION: We have developed by international consensus a scoring system to assess damage in patients with relapsing polychondritis. Following its validation, the RPDAM may contribute to improve the care of patients suffering from this rare condition as well as to standardize data collection for future clinical trials.