The authors have successfully developed an animal model of dual-phase bronchial responses and very high IgG titer by sensitizing Hartley-strain male guinea pigs. Specific airway resistance, which was determined in a two-chamber body plethysmograph, was elevated to sevenfold during immediate response, followed by a late phase response with a smaller but marked elevation in resistance. Furthermore, hematological and histological examinations revealed that the total cell count increased in BAL obtained during both immediate and late bronchial responses as compared to pre-OVA challenges. A significant increase in BAL eosinophils was present only for the late bronchial samples, and this finding was supported by histological examination.