Pulmonary arterial hypertension is a rare and often devastating disease, although various effective therapies are now available. Clinical trials have used hemodynamic, cardiac imaging, laboratory, and exercise measurements as surrogate and intermediate end points in pulmonary arterial hypertension. Yet, based on the current literature, it is difficult to surmise which of these (if any) have been definitively validated. In addition, investigators have advocated the use of combined clinical end points in future clinical trials. The dependence of clinical trials and clinical management on such end points warrants a review of their use.