A nationwide survey on the prevalence and risk factors for perennial allergic rhinitis in Korea was conducted by means of physical examination by otolaryngologists from July to October 1991. The total number of subjects examined was 9069 and they were drawn from 2899 households in 60 different districts throughout the country. The overall prevalence of perennial allergic rhinitis was 1.14%. For the evaluation of risk factors for perennial allergic rhinitis, a case-control analysis was carried out. The prevalence was influenced by age and urban or rural province. Risk factors such as current urban residence, urban birth place, overcrowding, higher educational attainment, nasal septal deformity and chronic sinusitis with nasal polyposis, indicated an increased risk of perennial allergic rhinitis. Other factors such as smoking and personal factors showed little influence on prevalence.