Granulomas were found in the lungs of 21 consecutive patients with stage I sarcoidosis who underwent open lung biopsy. The extent of granulomatous disease and fibrosis was significantly less (P less than .05) than seen in open lung biopsies from larger groups of patients with stage II and stage III sarcoidosis. The results of this study support what had previously been widely suspected: that is, if sufficient lung tissue is studied microscopically, granulomas will be found in the lungs of all patients having sarcoidosis with mediastinal lymphadenopathy but not radiographically demonstrable lung abnormalities.