By obtaining five transbronchoscopic biopsies of the lung from each of the right upper and lower lobes, the diagnosis of sarcoidosis was made in 36 of 37 prospectively studied patients. The diagnosis was made in all ten patients with stage-1 disease, but seven of the ten showed diagnostic tissue from only one lobe. Only one of the ten biopsies was diagnostic in four of those patients with a stage-1 disease. In disease of stage 2 and 3, there was good correlation between diagnostic biopsies and the radiographic distribution of infiltrates. Biopsies from the predominantly rather than the lesser involved lobe proved the diagnosis in all of these patients, except for the two patients with nodular sarcoid. We conclude that ten biopsies are optimal for obtaining the diagnosis in stage-1 disease; however, five biopsies may be adequate in non-nodular disease of stage 2 and 3 if the biopsies are of the lobe predominantly involved on the roentgenogram of the chest.