Cardiopulmonary exercise testing is a method used to assess the exercise capacity. It is used in cardiology to define the diagnostic and prognostic information, the treatment and its effectiveness. This method is also useful in sport medicine and in occupational medicine. The cardiopulmonary exercise test involves measuring of gas exchange during exercise testing. The article presents the main parameters assessed during the test and the indications and contraindications for conducting the test. It also reveals the results of recently published clinical trials on the use of cardiopulmonary exercise test in patients with cardiovascular disease and in the working population. The study included variability of respiratory parameters during the cardiopulmonary exercise test and after its completion, as well as their impact on the prognostic value. In addition, the results of a study involving an optimal choice of interval training on the basis of oxygen consumption at peak exercise are summarized.