We performed lung function tests and measurement of unspecific BHR to histamine in 28 patients with left heart insufficiency in the course of mitral valve disease. The patients were divided into two groups: Group I--persons qualified to mitral valve replacement, Group II--patients with restenosis after previous commissurotomy or never qualified to the operative treatment. We found any statistic significant differences in lung function parameters between both groups. We found an increase in BHR in almost all patients; BHR was markedly higher in the group II (p < 0.001). BHR did not correlate with lung function but a degree of correlation was found between BHR and the patients age.