This cross-sectional study evaluated the prevalence of, and risk factors for, asthma and rhinitis in a randomized sample of males and females, aged 0-69 yrs, in Perugia, Italy. To determine the prevalence of asthma and rhinitis, 824 subjects were interviewed by trained physicians using a modified American Thoracic Society and National Heart and Lung Institute-Division of Lung Disease questionnaire proposed in 1978 (ATS-DLD-78). Skin-prick tests were carried out in 667 subjects > or = 3 yrs of age. Age, sex, atopy, smoking, and household pets were considered potential risk factors for the development of asthma and rhinitis. Cumulative prevalences of: asthma was 8.1%; current asthma 5.0%; and rhinitis 15.2%. Positive skin tests were observed in 21.3% of subjects: in 63.4% of the cases of current asthma and in 68.7% of rhinitis cases. The prevalence of asthma and rhinitis was similar in both sexes. Prevalence of current asthma was almost three times higher in childhood than after the age of 10 yrs. Positive skin tests for pollens and house dust mite were the most prevalent risk factors for asthma. Current smoking was inversely associated with prevalence of current asthma possibly because of a self-selecting effect. Household pets were found not to be major risk factors for asthma or rhinitis. In conclusion, prevalence of asthma and rhinitis is a common health problem in the Perugia area, and atopy, particularly pollen sensitivity, is the most important risk factor for the development of asthma and rhinitis.