Several mouse monoclonal antibodies (MAbs) were obtained which specifically recognized allergen molecules from cat dander extract. Two of them (C5.8 and C5.24) were specific for the main cat allergen, Fel d I. One (C5.25) recognized an important allergen with approximate molecular weight of 30000 Da and a pI between 3.9 and 4.3. A third group of MAbs comprised several hybridomas which were specific either for cat albumin or cat immunoglobulin. The immunochemical characterization and the clinical significance of the cat dander components recognized by these MAbs is presented and discussed.