Background: Respiratory allergy is influenced and determined by genetic and environmental factors. Migration is a good epidemiological model to indirectly assess the influence of the environment. We assessed the clinical characteristics of respiratory allergy in immigrants in Brescia, Italy. Methods: We prospectively collected the data of all immigrants referred to our allergy service for respiratory complaints since 1992. All patients underwent a standard diagnostic workup. The records of a matched Italian population of 1,534 patients were examined for comparison. Results: Two hundred and thirty-seven patients were evaluated (108 male, mean age 36.3 years). Their countries of origin were uniformly distributed among 4 macroareas (Asia, Africa, South America, Eastern Europe). All patients were referred less than 1 month after the onset of symptoms. Family history for atopy was positive in 9% and clinical history of respiratory allergy was positive in 2%. The mean time of onset of symptoms after immigration was 5.21 years, and the onset symptoms were rhinitis and asthma in 68% patients. Twenty-five percent were monosensitized subjects and 20% of patients had cockroach positivity. Some characteristics (family history, previous clinical history and severity of rhinitis) were clearly different from those of the Italian control population. Conclusion: In this population of immigrants, it seems that environmental factors, more than genetic ones, play a role in the onset of respiratory allergy.