Sarcoidosis of the lung is a heterogeneous granulomatous and rare disease of unknown cause with a highly variable prevalence world-wide. It can involve any organ but affects in > 90% of all cases the lung. Particularly early stages are only incidentally discovered. Diagnostic work-up includes high-resolution chest CT, bronchoscopy with BAL (broncho-alveolar lavage) and biopsy sampling of the bronchi, the lung and/or lymph nodes of the mediastinum. Extensive disease on high-resolution CT, impaired lung function and pulmonary hypertension are predictors of poor outcomes. In the year of diagnosis quarterly controls are necessary due to the highly variable clinical course, which can be extended in stable patients after one year of observation. Corticosteroids are the most common first-line treatment. Patients unresponsive to corticosteroids may be treated with immunosuppressive agents either alone or in combination. End stage patients with lung fibrosis may become lung transplant candidates.