Health status is increasingly used in clinical practice to quantify symptom burden and as a clinical trial endpoint in patients with interstitial lung disease (ILD). The Kings Brief Interstitial Lung Disease (KBILD) questionnaire is a brief validated 15-item, disease-specific, health-related quality of life questionnaire that is increasingly used in clinical trials, but little data exist regarding the minimum clinically important difference (MCID). Using pulmonary rehabilitation as a model, we aimed to determine responsiveness of the KBILD and provide estimates of the MCID.KBILD, Chronic Respiratory Questionnaire (CRQ), Medical Research Council dyspnoea scale (MRC) and incremental shuttle walk test (ISW) were measured in 209 patients with ILD (105 with idiopathic pulmonary fibrosis (IPF)) before and after an outpatient pulmonary rehabilitation programme. Changes with intervention and Cohen's effect size were calculated. Anchor- (linear regression and Receiver Operating Characteristic plots) or distribution-based approaches (0.5 * standard deviation, standard error of measurement) were used to estimate the MCID of KBILD domain and total scores.KBILD, CRQ, MRC and ISW improved with intervention and the effect sizes of KBILD domain and total scores ranged from 0.28 to 0.38. Using anchor-based estimates, the MCID estimate for KBILD-Psychological, KBILD-Breathlessness and activities and KBILD-Total score were 5.4, 4.4 and 3.9 respectively. Using distribution-based methods, the MCID estimate for KBILD-Chest symptoms was 9.8. The MCID estimates for KBILD in IPF patients were similar.In patients with ILD and IPF, KBILD is responsive to intervention with an estimated MCID of 3.9 for the total score.