This study was carried out on 96 atopic patients with monosensitization against Dermatophagoides pteronyssinus and 30 control individuals. The patients were divided into 3 subgroups: 27 asymptomatic patients, 27 patients who only presented nasal symptomatology, and 27 patients with marked bronchial symptomatology. Total serum IgE, antigen-specific histamine release, and the number of beta 2-adrenergic receptors in peripheral blood lymphocytes in all patients were determined. The control group presented the highest number of beta-receptors in comparison with the bronchial symptomatic and nasal symptomatic patients. However, asymptomatic patients presented numbers of beta-receptors similar to controls, with no significant differences between both groups. No significant correlation was found between beta-adrenergic receptors and levels of total serum IgE. On the other hand, correlation between beta-receptors and specific histamine release was detected only in symptomatic nasal patients. It can be postulated that the decrease in beta-receptors is a consequence, and not the cause, of atopy.