The aim of the study was to study the possible pathogenetic mechanisms of the formation of bronchial hyperreactivity in bronchial asthma associated with microelementoses. The study group consisted of 45 children with bronchial asthma. The research methods were the method of neutron activation analysis of the content of trace elements in hair and the method of atomic absorption spectrometry of blood serum. The state of bronchial hyperreactivity was accompanied by a deficiency of essential microelements (69.6%) in severe bronchial asthma, against the background of selenium and zinc deficiency (plasma levels below 0.2 and 0.35 mg/l, respectively), and a decrease in the speed parameters of the function of external respiration.