Heart transplantation has recently become an accepted method of treating heart failure patients, also in Poland. Criteria of patient selection to heart transplantation and follow-up was based (and in some centers still is) on the assessment of the patients' clinical status according to NYHA classification and on the data on the extend of myocardial damage obtained from echocardiography or ventriculography at rest. However, examinations performed in the resting state do not provide complete information on the patient's clinical status, especially during increased oxygen demand. Recently cardiopulmonary exercise testing (CPX-to measure maximal oxygen consumption) has been increasing used to establish the prognosis in patients with severe heart failure and to define indications to heart transplantation. CPX combines exercise testing with monitoring the air flow and gas exchange. The measurement of oxygen uptake and anaerobic threshold during exercise is an objective, reproducible, safe and non-invasive method to assess cardiac reserve. There is evidence implying that in heart failure patients VO2max is a good short-term indicator of mortality and that its deterioration frequently precedes clinical decompensation. Thus, the parameter may be useful not only in defining the indications, but also in the monitoring the patient's clinical state and timing of heart transplantation.