BACKGROUND: The occupational contact dermatitis disease severity index (ODDI) was designed to assess the severity and importantly the functional disability caused by occupational contact dermatitis (OCD) of the hands in patients attending our occupational dermatology clinic. OBJECTIVES: To investigate the accuracy of the ODDI. PATIENTS/METHODS: Of 205 patients, 95 were assessed as having OCD of the hands. Content validity was assessed by content mapping and expert opinion. Construct validity was examined through comparing the ODDI against global clinical dermatology severity assessment (GCDSA). Intraobserver reliability, interobserver reliability, internal consistency, acceptability and convenience were also assessed. RESULTS: The ODDI was found to have content validity by the experts and was moderately correlated with GCDSA, supporting construct validity (Pearson's r = 0.54; P < or = 0.01). The ODDI was shown to be reliable with substantial agreement for both intraobserver reliability [intraclass correlation coefficient (ICC) = 0.62] and interobserver reliability (ICC = 0.75). Internal consistency within the ODDI was almost perfect (ICC = 0.94-0.99) and user survey showed the ODDI to be acceptable, easy and quick to use. CONCLUSIONS: The ODDI is a valid and reliable instrument to assess the severity and functional limitations caused by OCD, in patients who have had treatment or modified work duties, associated with some improvement of their dermatitis.