Spirometry was performed for subjects aged >40 years according to the guidelines of the American Thoracic Society/European Respiratory Society, using a spirometry system (model 1022; SensorMedics Corporation San Diego, CA). Predicted values were calculated using the predictive equation for the Korean population. Chest radiographs were evaluated and interpreted by a pulmonologist and a radiologist. Quality of life was measured using a validated Korean version of the 5-item self-administered EuroQOL (EQ-5D). An otorhinolaryngologic examinations were performed by trained otorhinolaryngologists according to standardized protocols. Examinations of the nasal cavity were performed using a 4 mm, 0° nasal endoscope before and after decongestion. Laryngoscopic vocal cord examinations were performed using a 4 mm 70° angled rigid endoscope with a CCD camera. The Epidemiologic Survey Committee of the Korean Otorhinolaryngologic Society prepared a protocol for the diagnosis of chronic laryngitis. This committee verified the quality of the survey by periodically visiting the mobile examination units, educating participating doctors, obtaining laryngeal examination data, and data-proofing using video documentation of the larynx throughout the study. Two otorhinolaryngologic surgeons from the Korean Otorhinolaryngologic Society subsequently confirmed the video documentation and assessed the disease decision protocol. Documentation of the video was obtained as 640 × 480-sized Audio Video Interleave files, which were compressed by DivX 4.12 codec using a compression rate of 6 Mb/s.