In adult patients with different variants of the complicated course of bronchitis (prolonged, relapsing, chronic) respiratory syncytial (RS) virus infections were shown to occur very frequently (37-72%, depending on the form on bronchitis). In 220 cases of RS infection the content of anti-RS-virus IgE in the blood was analyzed. The reaction of specific IgE was more pronounced in RS infection observed in patients with acute of bronchitis, than in those with chronic forms. The occurrence of RS-virus infections and reinfections was shown to be directly related to the presence of the broncho-obstructive syndrome in patients. The direct correlation between high levels of serum anti-RS-virus IgE and the presence of bronchospasms in patients, revealed in this study, was indicative of the possible pathogenetic role of this immunoglobulin: the Pearson association factor (rA) was 0.32, p < 0.01. Depending on the specific features of the clinical course of bronchitis, differences in the dynamics and speed on immune response, in the duration of the preservation of anti-RS-virus IgE in the blood, as well as in the character of the reaction of this immunoglobulin to single and multiple RS-virus lesion, were observed.