Cardiopulmonary exertion testing (CPET) is a non-invasive diagnostic method for monitoring of cardiopulmonary response to the load. This test enables evaluation of the function and capacity of the cardiovascular, pulmonary and metabolic system. (1) Therefore, ergospirometry has become an important clinical tool for assessing physical ability in patients with heart failure and other cardiorespiratory conditions. Ergospirometry test is considered the gold standard in testing of the functional abilities of cardiorespiratory system and planning individualized physical activity for patients undergoing cardiologic rehabilitation. The nurse has an integral role in the implementation of ergospirometry testing. In addition to helping patients manage their cardiovascular problems, her tasks are also the proper preparation of the room, equipment, and patient for an optimal test performance. During the test, occurrence of symptoms/complications such as fatigue, heart arrhythmia and syncope are possible. Therefore, the nurse working in the ergospirometry laboratory should know very well indications and contraindications for the test and should be skilled in cardiopulmonary resuscitation. Much of the sister’s work in ergospirometry takes place long before the diagnostic test is carried out. Continuous education, development of medical and psychological skills is an integral part of work and progress in the ergometric laboratory.