Mechanography was used to study contractile reaction of airway smooth muscles in experimental bronchial asthma in intact guinea-pigs and those incubated with IL-5. Development of experimental bronchial asthma (BA) in the animals leads to enhancement of contractile reactions of bronchial smooth muscles in response to histamine action. The exposure to IL-5 of the preparations of bronchial smooth muscles increases histamine-mediated bronchial contractility. This may explain the phenomenon of IL-5-mediated bronchial hyperreactivity in the absence of eosinophilic damage to the tissues. Expression of mRNA of IL-5 receptor alpha-chain suggests that development of IL-5-mediated hypersensitivity of bronchial smooth muscles occurs due to the presence of a relevant IL-5 receptor on their surface.