It is known that IFN-γ, T-cell lymphokine, suppresses IgE synthesis and enhances leukotrienes synthesis, and plays an important role in the allergic reactions of a bronchial asthma attack. It is reported that IFN-γ production from peripheral blood mononuclear cells(PBMC) induced by phytohemagglutinin was decreased in atopic subjects compared with normal subjects. In fact, some bronchial asthmatics do not have atopic features, and sometimes they display severe symptoms. Therefore, IFN-γ production from PBMC induced by Candida or mite antigen was studied in bronchal asthmatics. The results were as follows : (1) There was no significant difference in IFN-γ production between asthmatics and normal subjects. Among asthmatics, non-atopic asthmatics showed higher levels of IFN-γ production compared with atopic asthmatics. (2) Severe asthmatics showed high levels of IFN-γ production compared with mild and moderate asthmatics and normal subjects in Candida antigen stimulation. (3) High levels of IFN-γ production was observed in asthmatics with late asthmatic response to Candida antigen inhalation compared to asthmatics with no airway response and healthy controls. These results indicate that IFN-γ plays an important role in non-atopic and severe asthma attack and late asthmatic response to Candida antigen inhalation.