We used a body plethysmograph to determine airway resistances in 485 cases of laryngeal and tracheal stenoses. 143 cases who had resistances exceeding 60 mm H2O/l·a·sec underwent surgery. A vocal cord was laterally fixed in 49 patients suffering from bilateral recurrent paralysis. Optimal results were obtained at a postoperative resistance level of 30 mm H2O/l·a·sec (standard value: 14.77 ± 6.53 – n = 387). The patients could carry out work of medium intensity and had a steady voice. We performed tracheal interventions in 94 cases of tracheal stenoses. A mean postoperative resistance of 29.9 mm H2O /l·a·sec, with a tracheal diameter of 7–8 mm was attained. In practice, only a few patients found the remaining obstruction a hindrance, during work of maximal intensity. No recurrences were observed after treatment. Airway resistances exceeding 150 mm H2O /l·a·sec were found in 13 new admissions and 73 times in those undergoing therapy. In these cases, asphyxiation threatens. These patients must be tracheo-tomized or intubated immediatly.