Dyspnea and fatigue, the two most common symptoms experienced by patients with chronic obstructive pulmonary disease, are believed to result in decreased activity levels and poor quality of life. The primary measurable benefits of pulmonary rehabilitation to date have been a decrease in symptoms (mainly dyspnea and fatigue) and an increase in exercise endurance. The precise means by which pulmonary rehabilitation improves these, symptoms is not clear. The use of standardized questionnaires to measure the changes associated with pulmonary rehabilitation is important if we are to understand the magnitude of improvement with the intervention and determine those who will benefit. This article reviews the mechanisms believed to contribute to these symptoms and the methods available for their measurement.