One hundred and fifty-nine patients with Pulmonary Sarcoidosis have been studied ten to 20 years after diagnosis with a 90 per cent follow-up of survivors. Among the 76 patients with a mean follow-up of 22.5 years there is radiological evidence of pulmonary fibrosis in 13 and respiratory function tests revealed 12 with a transfer factor of less than 80 per cent of predicted. Of the further 83 patients followed to ten years there was radiological evidence of pulmonary fibrosis in five and a reduced transfer factor in four. Thirty-one patients received Prednisolone for various complications due to Sarcoidosis. There is no evidence of late respiratory disability. The complications and causes of death at ten and 20 years are examined and among the latter eight developed various forms of malignant disease. Since 1973 a further 139 patients have been studied, i.e. a total of 298 and two of these died from progressive Sarcoidosis despite corticosteroid treatment. Six patients have developed late autoimmune diseases.