BACKGROUND: Little is known about the epidemiology of rhinitis, particularly the perennial and non-allergic forms. The aim of this study was to compare the symptoms, atopic state, and medical history of individuals with seasonal and perennial rhinitis. DESIGN: Of 7702 adults aged 16-65 years registered with a London general practice, 2969 (30%) were screened by postal questionnaire. Samples of 113 subjects without rhinitis, 51 with seasonal symptoms alone, 128 with perennial symptoms and seasonal exacerbations were then interviewed. Atopic and non-atopic subjects were distinguished by skinprick testing with five common allergens. RESULTS: The estimated minimum prevalence of rhinitis was 24%: 3% had seasonal symptoms only, of whom 78% were atopic; 13% had perennial symptoms only, of whom 50% were atopic; and 8% had perennial symptoms with seasonal exacerbations, of whom 68% were atopic. Seasonal rhinitis was characterised by sneezing, itching, and a high prevalence of diurnal variation in symptoms. The most common provoking factors were dust, pollens, and infections. By comparison, perennial rhinitis was characterised by a higher prevalence of nasal blockage and catarrh, and a lower prevalence of diurnal variation and provocation by pollen. There were no significant differences among the groups in the sociodemographic characteristics examined. Subjects with seasonal rhinitis were more likely to be atopic and to have eczema and a family history of hayfever than those without rhinitis. Those with perennial rhinitis were more likely to have past or current eczema or migraine, be wheezy or labelled asthmatic, or have a family history of nose trouble other than hayfever. Subjects with both seasonal and perennial symptoms presented an intermediate clinical picture. CONCLUSIONS: Seasonal and perennial rhinitis differ in their atopic state, clinical presentation, and medical history. The extent to which these differences are genetically or environmentally determined requires further investigation.