Randomly assigned 119 adults with chronic obstructive pulmonary disease to an 8-week comprehensive rehabilitation program or to an 8-week education control program. Comprehensive pulmonary rehabilitation included education, physical and respiratory therapy instruction, psychosocial support, and supervised exercise training; education control included biweekly classroom instruction and discussions on respiratory therapy, medical aspects of lung disease, clinical pharmacology, and diet, but no exercise training. Both groups received extensive physiological and psychosocial evaluation before and after the intervention. Six months after enrollment, patients randomly assigned to the rehabilitation program showed significant increases in exercise endurance, whereas patients randomly assigned to control program showed nonsignificant increases. Improvement in self-efficacy was correlated with improvements in exercise endurance.