Clinical and experimental studies suggest that bosentan could delay the progression of interstitial lung disease (ILD) associated with systemic sclerosis (SSc), a condition for which no established efficacious treatment is available. The present trial investigates a possible use of oral bosentan, which is currently approved for the treatment of symptoms of pulmonary arterial hypertension (PAH) WHO Class III and IV, to a new category of patients suffering from ILD associated with SSc.