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The aim of this study was to determine and to evaluate silica induced lung cell reactivity--if any--in bronchoalveolar space, before clinical changes develop. Bronchoalveolar lavage (BAL) was carried out in 15 nonsmoking individuals with chronic professional silica exposure, free of lung signs and symptoms. Controls were healthy nonsmokers. Routine BAL cytology (HE, MGG) was completed by mast cell staining (toluidine blue). BAL lymphocyte subsets were phenotyped by direct two- and three-color immunofluorescence (applied DAKO A/S monoclonal antibodies: anti-CD3, CD4, CD8, CD11b, CD14, CD15, CD16 + 56, CD19, CD25, CD45, HLA-DR). Parallel staining was performed in peripheral blood. In individuals with chronic silica exposure we found: significant increase in alveolar macrophage (362 +/- 45 vs 160 +/- 33 x 10(3) cells/ml, p < 0.05), lymphocyte (61 +/- 9 vs 24 +/- 5 x 10(3) cells/ml, p < 0.05) and BAL total cell (415 +/- 76 vs 187 +/- 34 x 10(3) cells/ml, p < 0.05) numbers; significant increase in mast cell (0.4 +/- 0.1 vs 0.2 +/- 0.1, p < 0.05), NK cell (7.0 +/- 1.8 vs 3.6 +/- 1.0, p < 0.05) and Th early activated lymphocyte percent (CD4 + CD25+ calculated as percentage of CD4+ cells: 15.1 +/- 1.5 vs 7.8 +/- 1.6, p < 0.01). All results were presented as median +/- SEM. Bronchoalveolar space of people with chronic silica exposure usually shows pathological reaction (especially macrophagic alveolitis), although they are free of manifested pulmonary disease. Th early activated lymphocytes, NK cells and mast cells seem to play important role in the early interstitial lung tissue reaction to silica.