A study about the frequency of respiratory and allergic disorders in childhood was carried out in Rome, during the 2000-2001 school year. This survey represents the Italian contribution to the second phase of the International Study on Asthma and Allergies in Childhood (ISAAC Phase Two). A properly filled in ISAAC Phase II questionnaire was returned by parents of 1,760 children attending the fifth grade in primary school (83.5% of the target). Prick tests were performed to provide an objective measure of atopy, defined as skin reactivity to one or more allergens. The presence of visible flexural dermatitis was determined through skin examination. Lifetime prevalence for asthma, allergic rhinitis and eczema was 12.4%, 13.2% and 15.1%, respectively. Period prevalence in the last 12 months was 7.0% for attacks of wheezing or whistling in the chest, 9.1% for rhinitis symptoms, and 9.5% for dermatitis symptoms. A total of 1.6% of the children under examination had a visible flexural dermatitis. Of the children who performed prick test, 31.8% was skin positive at least to one of the adopted allergens. An international comparison with the results of other ISAAC Phase Two studies (conducted in Albania, Germany, Hong Kong, UK and Sweden) has shown that Rome and Hong Kong were the areas with the highest prevalence rate for atopy, but had comparatively low proportions of asthmatic subjects. This inconsistency suggests that factors other than atopy could be responsible for the geographic epidemiological distribution of asthma.