An alternative procedure to evaluate plethysmographic tracings is described for the determination of airway resistance (Raw) and specific airway conductance (SGaw). Raw and SGaw obtained with this method reflect the average resistive impedance over one breathing cycle. Although both work and apparative expenditures are minimal, the results are well comparable with those calculated with more involved methods. The technique is particularly well suited for patients with impaired cooperation since SGaw can be determined without measuring the intrathoracic gas volume.