The measurement of the O2 status of the human organism, the knowledge of factors which influence it and the using and development, respectively, of measures for its permanent improvement are of great importance for the prevention diagnosis, prophylaxis and therapy. The O2-intake in rest of the organism is regarded as absolute characteristic of the oxygen status. In investigations of the dynamics of the status it is in most cases sufficient to use the arteriovenous Hb-O2 saturation difference as relative distinctive mark, the representative determination of which from routine measurements of pO2 in rest is discussed. From such measurements the strong dynamics of the O2 status was found. Apart from the deterioration with growing age the deterioration by stressor influences of different kind, in hyposthenias and the minima in the 24-hour-cycle were established. Improvements were measured after perseverance training and after treatments with processes of the oxygen multistep therapy. After discussion of the three basic steps of this therapy the 36-h-O2-multistep process and the 15-min-O2-multistep rapid process are mentioned as standard variants which are to be used ambulatorily. The rapid process is entered more in detail and the practice of its performance as well as the results of measurements of the typical pO2 in rest before and after these processes are discussed. Surprising is the existence of the increase effected of the arterial pO2 in rest and of the decrease of the venous pO2 in rest for weeks, months up to years.(ABSTRACT TRUNCATED AT 250 WORDS)