Assessment of patient perception of disability and outcomes from treatment has become an integral part of medical care. General quality-of-life measurement tools have led to the development of disease-specific quality instruments. Conventional methods for evaluating nasal-sinus disease are inadequate to assess the impact of these disorders on everyday life. Therefore, using methods that are well established and validated for creating instruments, the Rhinosinusitis Disability. Index was created to evaluate the self-perceived impact of disease-specific head and neck disorders. The development of the preliminary and final versions (30 items) of the Rhinosinusitis Disability Index is described. Content-related validity using Cronbach's alpha measurement and construct-related validity were accomplished. A comparison of the responses between patients with and without documented nasal or sinus disease was used to verify that the Rhinosinusitis Disability Index is a valid measuring instrument for patients with sinus disease, and test-retest validity reveals reliability over time.