Heart failure (HF) is characterised by poor prognosis and increasing prevalence regardless of the progression in diagnosis and therapy. A hallmark of HF is a reduced ability to perform physical exercise. Pathophysiology of impaired exercise capacity is complex; the basis is pump failure central mechanism but peripheral responses are also affected. For an exercise tolerance assessment self-administered activity questionnaires, like functional NYHA classification, are used. Exercise testing has been widely used in assessment of chronic, stable HF patients (pts). Cardiopulmonary exercise test (CPX) and direct measurement of maximal oxygen uptake (VO2max) is established as a mainstay of the objective evaluation of functional activity in HF. Rest echocardiography is of limited value in predicting exercise tolerance. Both systolic and diastolic function can be assessed by stress echocardiography. Non-invasive estimation of left and right ventricular filling pressure is well correlated with exercise duration and VO2max. HF is not a contraindication for exercise training and cardiac rehabilitation. However, careful pts selection, supervision during exercise and follow-up are mandatory. The benefits of exercise training in HF pts include improvement in exercise duration, quality of life and mortality reduction.