Cardiopulmonary exercise testing (CPET) is an important diagnostic tool in contemporary clinical practice. This document presents an expert opinion from the Working Group on Cardiac Rehabilitation and Exercise Physiology of the Polish Cardiac Society concerning the indications, performance technique, and interpretation of results for CPET in adult cardiology. CPET is an electrocardiographic exercise test expanded with exercise evaluation of ventilatory and gas exchange parameters. It allows for a global assessment of the exercise performance including the pulmonary, cardiovascular, hematopoietic, neuropsychological, and musculoskeletal systems. It provides a noninvasive dynamic evaluation during exercise and is a reference modality for exercise capacity assessment. Moreover, it allows the measurement of numerous prognostic parameters. It is useful in cardiology, pulmonology, oncology, perioperative assessment, rehabilitation as well as in sports medicine and in the evaluation of healthy people. This test not only helps to diagnose the causes of exercise intolerance but also supports the evaluation of the treatment. New opportunities are offered by combining CPET with imaging such as exercise stress echocardiography. These tests are complementary and synergistic in their diagnostic and prognostic strength.