Pulmonary inflammation has been evaluated in 43 crocidolite-exposed asbestos (ASB) workers and 12 control subjects, using a quantitative index of gallium uptake (GI). The GI was compared with chest roentgenographs (CXRs) graded by the ILO classification. The ASB workers included 15 with asbestosis (CXR greater than or equal to 1/0), 19 with a normal CXR (CXR 0/0), and 9 with equivocal CXR changes (CXR 0/1). In individuals with asbestosis the GI was 3.6 +/- 0.3 (mean +/- SEM), P less than 0.01 compared with exposed patients without asbestosis. In exposed patients with equivocal CXR changes (0/1) the GI was 3.1 +/- 0.3, and in exposed patients with a normal CXR (0/0) the GI was 2.4 +/- 0.2. The GI for subjects without lung disease was 1.2 +/- 0.2, P less than 0.01 compared with exposed patients without asbestosis. The scans were scored independently by two observers, and the correlation coefficient of the two sets of GI was 0.95. These data demonstrate that subjects with crocidolite-induced asbestosis and exposed patients with equivocal CXR changes or a normal CXR have significantly increased GI.