The pulmonary fixation of Gallium 67 has been studied by broncho-alveolar lavage (LBA) in a group of 10 cases of stage II pulmonary sarcoid, proven histologically, and in a group of 11 cases of idiopathic diffuse interstitial fibrosis (FID). The pulmonary activity of Gallium 67 was measured in vitro in a quantitative manner on a centrifuged clump and a supernatant of LBA as well as on the serum and in vivo in a semi-quantitative manner by the Line index. The alveolar Gallium activity has been correlated with different cytological and biochemical parameters of the lavage liquid. There was a narrow correlation in the serum between the Gallium 67 activity and the level of circulating transferrin. The fixation of Gallium in the cellular clump of LBA depends on the number of macrophages present in the clump and the total available radioactivity. The macrophages of the sarcoid and fibrosis cases picked up the gallium in a similar fashion, with an affinity all the more important as the total available radioactivity was weak. The radioactivity of the supernatant of the lavage liquid was quantitatively important and narrowly tied to the diffusible proteins present in the lavage. There was no correlation between the semi-quantitative Line index and the cytological or biochemical data in the fibrosis cases. In the sarcoid cases there was an inverse correlation with the polymorphonuclear leukocyte count. The semi-quantitative index was only correlated with alveolar gallium fixation level in the fibrosis group.(ABSTRACT TRUNCATED AT 250 WORDS)