T-cell-derived lymphokine, IFN-gamma, has potent effects on B-cell differentiation and leukotriene C4 production in leukocytes, and inhibits the effect of IL-4 on IgE production. To investigate the role of IFN-gamma in the pathogenesis of bronchial asthma, we examined IFN-gamma production by peripheral blood mononuclear cells cultured with Candida antigen and serum Candida specific IgG1 antibody from 20 asthmatics. The results were as follows: 1) IFN-gamma production in non-atopic severe asthmatics was significantly higher than in healthy subjects, atopic mild and moderate asthmatics, and atopic severe asthmatics (p < 0.05). 2) There was a significant correlation between IFN-gamma production induced by Candida antigen and serum Candida specific IgG1 antibody (r = 0.72, p < 0.01). These results suggest that IFN-gamma may play an important role in the pathogenesis of non-atopic severe bronchial asthma.