For early diagnosis of lung diseases the plethysmographic measurement of IGV is important. The influences of gases in the abdomen as the influences of pressure swings between mouth and alveolar space were several times investigated and did not show clinical relevance. The position of the mouthpiece in relation to the measured person should be taken carefully into consideration. We compared for the measurement of the occlusion-angel, which allows the calculation of the IGV, the panting- with the breathing going-on method. On 42 persons there were no significant differences between the results (o different laboratories: painting--breathing going-on = 2.8 resp. -0.6%). We prepare the breathing going-on method because it seems better that the person does not change his breathing level what could happen during the otherwise necessary instruction of the person.