Dermatophagoides farinae, or the American house dust mite, is a common cause of allergy and asthma. Current tests for sensitization to D. farinae include an indirect enzyme-linked immunosorbent assay (ELISA) method for specific IgE detection, which, while clinically useful, is time-consuming and has low sensitivity since it uses crude mite extracts. We developed two new ELISA methods to detect the group 2 allergen from D. farinae (Der f 2) and the Der f 2-specific IgE in sera of patients with asthma. Using recombinant Der f 2 protein for the analysis of Der f 2-specific IgE, we tested both indirect ELISA and avidin biotin complex ELISA (ABC-ELISA) methods in 46 patients who were also tested by Pharmacia UniCap. Both of these approaches are more specific than traditional methods using crude mite extracts. These new tests could aid in the laboratory diagnosis of asthma due to sensitization to D. farinae.