Cardiopulmonary exercise testing (CPET), performed in a clinical laboratory setting, has long been used to evaluate persons with suspected or confirmed cardiopulmonary disease. This form of testing is now recognized as the gold standard for evaluating a person's aerobic exercise performance. In addition, simplified submaximal approaches to assessing functional capacity are readily available; perhaps the most recognized being the 6-min walk test. With the growing interest in CPET for evaluating patients with pulmonary artery hypertension (PAH), gaining a better understanding of the significance of the various outcomes used and how they are relevant to evaluating patients with PAH is a an important endeavor. This review highlights the utility of CPET; the various outcomes that can be derived from this assessment and the various functional tests commonly used as well as related tests that may have a role in clinical assessment of patients with PAH.