This study was designed to determine whether inspiratory resistive training could improve the exercise performance of patients with severe chronic airflow limitation who had already received optimum conventional therapy with bronchodilators and physiotherapy. Eighteen patients were studied. Ten patients were trained with an inspiratory resistance device for six weeks and eight patients used a placebo device. Psychological factors, likely to influence exercise capacity, were taken into account. Although there was no significant increase in maximum inspiratory pressure in the ten trained subjects, inspiratory muscle endurance was improved. Exercise performance, as assessed by progressive cycle exercise, stair climbing, 12 minute walking distance and treadmill walking did not change significantly in either group. It was concluded that inspiratory muscle training, using a currently available technique, produced no additional improvement in exercise capacity beyond that achieved by conventional bronchodilator and rehabilitation therapy.