Pirfenidone is approved in the EU for the treatment of mild to moderate Idiopathic Pulmonary Fibrosis (IPF), but not for other forms of progressive fibrotic lung diseases, in which anti-inflammatory therapy is not sufficiently effective. RELIEF, a randomized, double-blind, placebo-controlled, parallel-group, multi-center, phase II study, aims to explore the efficacy and safety of oral pirfenidone for progressive, non-IPF lung fibrosis. The study population comprises patients with collagen/vascular disease-associated lung fibrosis (CVD-LF), fibrotic non-specific interstitial pneumonia (fNSIP), chronic hypersensitivity pneumonitis (cHP), and asbestos-induced lung fibrosis (ALF). Disease progression has to be proven by slope calculation of at least three Forced Vital Capacity (FVC) measurements obtained within 6-24 months prior to inclusion, documenting an annualized decline in percent predicted FVC of 5 % (absolute). The study medication (pirfenidone or placebo) is administered on top of existing anti-inflammatory medication, which has to be stable for at least three month. As primary endpoint the efficacy will be assessed by the absolute change in percent predicted FVC from baseline to week 48 in the Pirfenidone and placebo group. Data will be analyzed using a rank analysis of covariance (ANCOVA) model. A number of secondary endpoints will be analyzed, e.g. time to disease worsening, progression-free survival, categorical relative change of FVC from baseline to week 48. Patient recruitment started in April 2016, currently 15 study centers including all five DZL sites. 59 (16 CVD-LF, 19 fNSIP, 21 cHP, 3 ALF) of 374 planned patients have been randomized so far (February 1, 2017).