Parameters of pulmonary function were measured at resting breathing rates (mean 15-17/min) and at breathing rates of 20-40/min in 238 subjects (79 normals, 44 patients with normal pulmonary function in spite of lung disease, and 115 patients, most of whom had obstructive-emphysematous lesions) in a constantvolume body plethysmograph with a respiratory bag. In the subjects with normal pulmonary function the resistance increased significantly by 25 and 45 percent, resp., with more rapid respiration (p smaller than 0,01). Nevertheless it is assumed that this rarely accounts for false interpretations in everyday routine practice. No relationship of breathing rate to respiratory passage resistance was observed in patients with increased total resistance. By way of contrast, ventilation work of breathing (pV diagram) and the index of ventilation work of breathing (defined Vp ratio) showed a close correlation to breathing rate in all 3 groups. This leads us to conclude that these parameters provide more exact information on the breathing mechanism than does total resistance. Studies on ventilation work of breathing must be conducted under clearly defined breathing rates and consideration of the respiratory volume. intrathoracic gas volume was not correlated to the breath rate.