Lung fibrosis is a complication of sarcoidosis, in which TGF-β/Smad pathway may play an important role. We evaluated gene expression of TGF-β1, SMAD2, 3 and 7 in bronchoalveolar lavage (BAL) cells and peripheral blood (PB) lymphocytes of sarcoidosis patients (n=94) to better understand the mechanisms of sarcoid inflammation. The relative gene expression was analyzed by qPCR method. Selected clinical/radiological features and biochemical markers were taken into account in the analysis. We found that TGF-β1 and SMAD3 expressions in PB lymphocytes were significantly higher in sarcoidosis patients. Up-regulation of SMAD7 (inhibitory Smad) and down-regulation of SMAD3 in BAL cells in all subgroups were found. The expression of TGF-β1 in PB lymphocytes was the highest in patients with lung parenchymal involvement and in the insidious onset phenotype. The expression of TGF-β1 in BAL cells was higher in patients with abnormal spirometry (p=0.012), and TGF-β1 and SMAD3 in patients with restrictive pattern (p=0.034 and 0.031, respectively). Several statistically significant negative correlations were found between the expression levels of SMAD2 and 3 in BAL cells and various LFT parameters. We conclude that TGF-β/Smad pathway is involved in the pathogenesis of pulmonary sarcoidosis. These biomarkers (especially TGF-β1, SMAD2 and 3) are of a negative prognostic value.