There are two primary treatment conditions. Patients with ILD are be randomized to either an intervention consisting of aerobic exercise training plus patient education or a control condition that includes patient education only. Aerobic exercise training will consist of a 10-week regimen of supervised treadmill walking three times a week. The duration of the exercise sessions will progress from 30 minutes to 45 minutes per session over the 10 weeks, as tolerated. The intensity of the exercise will be determined based on results of a cardiopulmonary exercise test. Those randomized to control will not initially engage in aerobic exercise training. There will, however, be a secondary study: a crossover design in which subjects in the control group will complete the aerobic exercise regimen.