CPET is the gold standard test for the integrated assessment of cardiovascular, respiratory, metabolic, and muscular responses to exercise. It allows for the quantification of functional capacity, identification of the limiting mechanism of exertion, and risk stratification in multiple clinical contexts. CPET is particularly useful in the evaluation of unexplained dyspnea, heart and lung disease, pulmonary hypertension, heart failure, interstitial lung disease, pre-operative assessment, and exercise prescription. It provides a unique pathophysiological view of exertion, allowing for accurate differential diagnosis, prognostic stratification, and personalized therapeutic guidance.