Sarcoidosis is a systemic granulomatous disorder of unknown genesis with an average annual incidence of 10/100,000 population in Denmark. The clinical picture and prognosis are dominated by the pulmonary changes in the majority of cases. The patho-anatomical picture consists of a T-lymphocyte-dominated interstitial inflammation with non-caseating epithelioid granulomas followed by fibrosis in varying degrees. The different types and courses of pulmonary disease are reviewed. Clinical examination, chest radiography, pulmonary function tests (especially the carbon dioxide diffusion capacity) and S-angiotensin-converting enzyme (S-ACE) are the most important measures of disease activity. The value of systemic corticosteroids is critically evaluated; most patients in this country can be observed without treatment because the spontaneous resolution rate is high. It is recommended that steroids should be administrated primarily in symptomatic and progressive parenchymal lung disease, or when critical or disabling extrathoracic sarcoidosis is present. If the pulmonary parenchymal infiltrates do not disappear within approximately 18 months, a course of prednisolone for at least one year should be considered to prevent disabling or even lethal pulmonary fibrosis.