Diurnal profiles of impulse oscillometry during 24 hours in 3 hour intervals in sitting and lateral lying position have been studied in 20 healthy female and male probands 10-67 years of age. Approximating the profiles by a sine-cosine-function the amplitude of resistance was found up to 3, that of reactance up to 1 hPa/l/s in single cases, preferably for end-expiratory values and for the resistance-flow- and the resistance-volume-gradients, more pronounced in lying than in sitting position. The daytime reaching maxima of resistance and minima of reactance is different in single individuals. Single persons with obviously high vitality or sensibility showed very high amplitudes reproducible within IOS measuring limits of 0.2 hPa/l/s after 6 months.