The allergic responses of 52 bronchial asthma patients who exhibited a positive bronchoprovocation test with house dust and 50 allergic rhinitis patients who had positive RAST results to Dermatophagoides farinae (D. farinae) were studied, including the measurement of D. farinae-specific IgE using D. farinae-RAST, total IgE and skin reactivity to D. farinae and house dust. A comparison between the allergic rhinitis group in which methacholine PC20 was more than 4.66 mg/mL and the allergic rhinitis group which presented negative results in the methacholine bronchial challenge test, indicated that there were significant differences in skin test reactivity and the ratio of specific IgE to total IgE (P less than .05). The allergic responses we observed were not different between the allergic rhinitis group in which methacholine PC20 was less than 4.66 mg/mL (asthmatic range of methacholine PC20) and the allergic rhinitis group in which methacholine PC20 was more than 4.66 mg/mL. When comparing the bronchial asthma group which showed positive results in D. farinae-RAST and the allergic rhinitis group in which methacholine PC20 was less than 4.66 mg/mL, significant differences were noted in total IgE level (P less than .05). These findings suggest that the development of bronchial asthma in patients with allergic rhinitis might be predicted by measuring the degree of bronchial hyperreactivity and their allergic responses.