The TCR repertoire and the CD4/CD8 ratio of clones from peripheral blood (PB), transbronchial biopsies (TBB), and bronchoalveolar lavage (BAL) of 16 sarcoid patients was analyzed by staining the clones with monoclonal antibodies against nine V beta-families. We observed a striking increase in the CD4/CD8 ratio of the clones from BAL; whereas the CD4/CD8 ratio of the clones from PB was in the normal range. The CD4/CD8 ratio of the TBB-clones had also increased, but this increase did not reach the level of that of the BAL clones. The most prominent changes in the V beta percentages could be detected in the CD4+ subpopulation of the BAL-clones. The most abundant V beta families were V beta 5 in PB and BAL (11.8 and 28.6%, respectively) and V beta 6 in the TBB (12.4%). A similar compartmentalized V beta usage could be demonstrated in one patient with tuberculosis and one patient with HP. The increase in V beta 5, V beta 8, V beta 12, V beta 13.3, and V beta 19 in the BAL and the increase of V beta 5, V beta 6, V beta 13.3, and V beta 19 in the TBB suggest an antigen-driven activation of the T cells in both compartments. Differences in the V beta percentages between BAL and TBB and the lower CD4/CD8 ratio in the TBB, however, demonstrate a relative independence of the two compartments.