To assess the usefulness of bronchoalveolar lavage (BAL) collagenase measurement in gauging disease severity and outcome in sarcoidosis, we analyzed BAL fluids from 84 patients with sarcoidosis for collagenase and monitored disease progress in these patients for a minimum of 12 months. Twenty patients (24%) were found to have BAL collagenase activity on initial evaluation (collagenase-positive group). Compared with patients without BAL collagenase (collagenase-negative group), the collagenase-positive group had (1) a higher proportion of BAL suppressor T cells (p less than 0.03); (2) a lower helper-suppressor T-cell ratio (p less than 0.002); (3) lower mean percent predicted FEV1, FVC, and DLCO levels (p less than 0.05); and (4) a higher proportion of patients with advanced (Stage 4) disease on chest roentgenogram (p less than 0.001). Significant differences were also observed between the collagenase-positive and collagenase-negative groups during follow-up. A higher proportion (55%, n = 11) of collagenase-positive patients required corticosteroid therapy than did collagenase-negative patients (26%; n = 17; p less than 0.025). Of those who remained untreated, pulmonary function tended to decrease in the collagenase-positive group, whereas mean pulmonary function levels actually improved in the collagenase negative group (p less than 0.05). Of those who required therapy, mean percent predicted FVC and DLCO levels improved significantly after treatment in the collagenase-negative group (p less than 0.01 and p less than 0.05, respectively), whereas an improvement in percent predicted FVC levels only (p less than 0.01) was observed in the collagenase-positive group.(ABSTRACT TRUNCATED AT 250 WORDS)