The influence of sauna on pulmonary functioning in patients with an obstructive pulmonary disease was studied in 12 male patients by measuring forced vital capacity (FVC) and forced expiratory volume in one second on seven measure points the day of the sauna program. Despite the fact that body cooling and changes in osmolality of bronchial liquid can induce bronchoconstriction, we measured a significant improvement of the lung function parameters: FVC values were 3.22 +/- 0.89 and 3.6 +/- 0.99 before and after the sauna program, respectively. It is concluded that patients with an obstructive pulmonary disease can take part in sauna programs without eliciting bronchoconstriction; sauna even causes transient improvement of the lung function.