In this study we assessed the effects of Dermatophagoides pteronyssinus (Dpt) rush immunotherapy in comparison with placebo treatment in our asthmatic patients. Fourteen highly Dpt-susceptible adults were randomized in two groups (immunotherapy and placebo) and treated in single-blind manner. Patients were selected according to the recommendation of the immunotherapy position paper (1993). To minimize side effects we modified the protocol by adjusting allergen doses for each patient separately. Immunologic (total and Dpt-specific serum IgE and IgG antibodies/EIA, Pharmacia) and clinical parameters (spirometry, medication score and skin testing) were recorded before treatment, after 2 weeks, at the second month and after 4 months of immunotherapy onset. None of the patients had life-threatening side effects in the course of the treatment. The results obtained demonstrated significant influence of immunotherapy on Dpt-specific serum IgG synthesis (Kruskal Wallis test, p < 0.05) and on the late phase skin reaction with Dpt (U-test, p < 0.05) at the end of the second month of immunotherapy onset. In the immunotherapy group, we also registered a negative correlation between concentrations of Dpt-specific serum IgE and IgG antibodies (p = -0.83; p < 0.05), at the end of the second month. In addition, diversities among patients, expressed by immunologic parameters, were related to the amount of delivered allergen. There were no significant differences between groups concerning medication score from opposite to better FEV, PEFR and dPEFR results (Kruskal Wallis, p < 0.05) in the placebo group. In conclusion, Dpt-specific serum IgG concentration, immunologic score and late phase skin reactivity to allergen appeared to be the valid parameters of rush-immunotherapy achievement, while delivered allergen dose also seemed to be an influencing factor.