The action of cardioactive substances is tested by repeated ergometric loads. The aim of the present work was to assess whether after previous loads in the organism certain adaptational changes persist, cardiovascular, respiratory or metabolic, which might influence the course of a subsequent load. The authors exposed therefore two groups of patients to identical loads after 2- or 24-hour intervals and investigated the behaviour of some spiroergometric indicators. From the results ensued that a load repeated after 2-hour intervals takes place under different conditions. In this participates probably the increase of the a-v difference for oxygen and to a smaller extent also adaptation of the respiratory system. Loads repeated after 24-hour intervals were comparable.