In patients with chronic fibrosing interstitial lung disease (ILD), a progressive fibrosing phenotype (PF-ILD) may develop, but information on the frequency and characteristics of this population outside clinical trials is lacking.We assessed the characteristics and outcomes of patients with PF-ILD other than idiopathic pulmonary fibrosis (IPF) in a real-world, single-centre clinical cohort. The files of all consecutive adult patients with fibrosing ILD (2010-2017) were retrospectively examined for predefined criteria of ≥10% fibrosis on high-resolution computed tomography and progressive disease during overlapping windows of 2 years. Baseline was defined as the date disease progression was identified. Patients receiving nintedanib or pirfenidone were censored from survival and progression analyses.In total, 1395 patients were screened; 617 had ILD other than IPF or combined pulmonary fibrosis and emphysema, and 168 had progressive fibrosing phenotypes. In 165 evaluable patients, median age was 61 years; 57% were women. Baseline mean forced vital capacity (FVC) was 74±22% of predicted. Median duration of follow-up was 46.2 months. Annualised FVC decline during the first year was estimated at 136±328 mL using a linear mixed model. Overall survival was 83% at 3 years and 72% at 5 years. Using multivariate Cox regression analysis, mortality was significantly associated with relative FVC decline ≥10% in the previous 24 months (p<0.05), age ≥50 years (p<0.01) and diagnosis subgroup (p<0.01).In this cohort of patients with PF-ILD not receiving antifibrotic therapy, the disease followed a course characterised by continued decline in lung function, which predicted mortality.