The effect of inspiratory resistive breathing training using a simple apparatus was tested in 27 optimally medicated consecutive outpatients with severe chronic airflow limitation, randomly assigned to a test and a control group. Patients trained in their homes for up to 10 min thrice daily and increments in resistance were made, if possible, every fortnight. The control group used the same apparatus, but without inspiratory resistance. Three months from the start of training, the following statistically significant differences between the 2 groups were observed: a marked decrease in dyspnea in the trained group, a 60% versus 22% rise in endurance time on a cycle ergometer at 2/3 of maximal work load, a fall in functional residual capacity, and a fall in respiratory frequency both at rest and during exercise.