To study the differences in bronchial responsiveness to inhaled methacholine and salbutamol between patients with mitral valve disease those with bronchial asthma a bronchial provocation test (Astograph) and pulmonary function tests were done in 25 patients with mitral stenosis (MS) and 18 patients with bronchial asthma (BA). We derived an index of airway reloxability from the effect of salbutamol after precontraction with inhaled methacholine. This index was the change in respiratory conductance (Grs) over time during inhalation of salbutamol (SGrs-d). It was computed as SGrd = delta Grs/delta t. Eighteen patients with MS (72%) showed bronchial hyperresponsiveness (BHR) to methacholine. The MS patients with BHR (MS(+)) had lower values of the ratio of the forced expiratory volume in one second to the forced vital capacity (FEV/FVC) and maximal expiratory flow at 25% of vital capacity (V25) than MS patients without BHR (MS(-)). There was a significant correlation between V25 and the log cumulative dose producing a 35% decrease in respiratory conductance (PD35Grs) in MS(+). The mean log Dmin of MS(+) was significantly higher than that of the patients with BA (0.14 +/- 0.64 log units and -0.30 +/- 0.65 log units, p < 0.05, respectively). The mean log PD35Grs of MS(+) was also significantly higher than that of the patients with BA (1.09 +/- 0.53 log units and 0.45 +/- 0.66 log units, p < 0.01, respectively). Indices of relaxability (SGrs-d and SCrs-d/Grs-d) in MS(+) were significantly lower than in BA patients. Indices of hyperresponsiveness and relaxability were both significantly lower in patients with MS than in patients with BA.(ABSTRACT TRUNCATED AT 250 WORDS)