The measurement of cardio-circulatory and gas-exchange parameters during phyยญ sical exercise - the so-called ergo spirometry or cardiopulmonary exercise testing (CPX) - as a basis of pathophysiological and clinical research has a long tradition in Cologne. Knipping and his coworkers, especially Hollmann, performed basic reยญ search work in healthy subjects. In the area of sports medicine, bicycle or treadmill exercise testing with parallel serial lactate determinations has gained increasing imยญ portance for the assessment of cardiac functional capacity. Also, in other medical disciplines, ergospirometry lost its importance. K. Wasserman in Los Angeles is to be credited for having further improved the method to its present standard, a computerized, on-line measuring and practicable cardiopulmonary exercise testing procedure. The prerequisites were technical innovations, such as continuouslyยญ measuring gas analyzers and personal computers. Thereby, the knowledge about physiology, pathophysiology, and clinical circumstances of cardiocirculatory and reยญ spiratory regulation during exercise were significantly extended. The working groups of W. Hollmann, Cologne, and K. Wasserman, Los Angeles, determined normal values for the gas-exchange parameters and derived values for healthy normals in large populations. Wasserman and coworkers were able to introduce a differential diagnostic concept for patients suffering from various cardiovascular and cardioยญ pulmonary diseases. Many cardiologists, working, for example in myocardial failure or with rate-adaptive pacemakers, belong to those who recommended the modem, computerized ergo spirometry. Furthermore, this method is controversely discussedยท by colleagues working in sports medicine and pulmonary function.