Even though a complex disease such as asthma does not have a comprehensive animal model, some characteristics can be duplicated in mice and guinea-pigs. The murine model offers advantages with respect to strain control and availability of molecular biology tools. We introduced the use of the BP2 ‘Biozzi’ mice, which have high IgE titres and expresses bronchopulmonary hyperresponsiveness (BHR) after a single antigenic provocation. BHR is accompanied by airway sequestration of lymphocytes and eosinophils, and by a newly described IgE-bearing granulocyte, identified to basophils. The murine model permits studies for cellular and molecular biology and to investigate the mode of action of drugs.