BACKGROUND:Uncertainty exists regarding the clinical relevance of exercise training across the range of interstitial lung diseases (ILDs). OBJECTIVE:To establish the impact of exercise training in patients with ILDs of differing aetiology and severity. METHODS:142 participants with ILD (61 idiopathic pulmonary fibrosis (IPF), 22 asbestosis, 23 connective tissue disease-related ILD (CTD-ILD) and 36 with other aetiologies) were randomised to either 8 weeks of supervised exercise training or usual care. Six-minute walk distance (6MWD), Chronic Respiratory Disease Questionnaire (CRDQ), St George Respiratory Questionnaire IPF-specific version (SGRQ-I) and modified Medical Research Council dyspnoea score were measured at baseline, 9 weeks and 6 months. MEASUREMENTS AND MAIN RESULTS:Exercise training significantly increased 6MWD (25 m, 95% CI 2 to 47 m) and health-related quality of life (CRDQ and SGRQ-I) in people with ILD. Larger improvements in 6MWD, CRDQ, SGRQ-I and dyspnoea occurred in asbestosis and IPF compared with CTD-ILD, but with few significant differences between subgroups. Benefits declined at 6 months except in CTD-ILD. Lower baseline 6MWD and worse baseline symptoms were associated with greater benefit in 6MWD and symptoms following training. Greater gains were seen in those whose exercise prescription was successfully progressed according to the protocol. At 6 months, sustained improvements in 6MWD and symptoms were associated with better baseline lung function and less pulmonary hypertension. CONCLUSIONS:Exercise training is effective in patients across the range of ILDs, with clinically meaningful benefits in asbestosis and IPF. Successful exercise progression maximises improvements and sustained treatment effects favour those with milder disease. TRIAL REGISTRATION NUMBER:Results, ACTRN12611000416998.