It is known that IFN-γ, T-cell lymphokine, has potent effects on immunoglobulin synthesis, leukotrienes synthesis and delayed-type hypersensitivity. These factors are thought to be closely related to allergic reactions in bronchial asthma. Therefore, IFN-γ production from peripheral blood mononuclear cells induced by Candida or mite antigen was examined in asthmatics, and relations with other lymphocytic functions were studied to eluciate the role of IFN-γ. The results were as follows : (1) There was a significant correlation between IFN-γ production and Candida specific serum IgG1 antibody. (2) There was a significant correlation between IFN-γ production and lymphocyte blastgenesis induced by Candida antigen. (3) High levels of IFN-γ production were observed in asthmatics with positive late phase or delayed phase skin reaction to Candida antigen compared to asthmatics with negative late phase or delayed phase skin reaction. (4) Asthmatics with positive Candida or mite specific IgE radioallergosorbent test(RAST) showed a low level of IFN-γ production compared to asthmatics with negative IgE RAST. These results indicate that asthmatics with low IgE antibody and activated lymphocytes show high levels of IFN-γ production, and in these low IgE asthmatics, IFN-γ may play an important role in the allergic reactions of bronchial asthma.