Introduction Over 100,000 Iranian war veterans suffer from chronic effect of mustard gas exposure. Sulfur mustard was used by Iraq during the Iraqi-imposed war on Iran(Between 1980-1988s). The major complaints of these patients are mild interstitial fibrosis and brochiolitis. We aimed to determine the state of fibrosis progression and assessed TGF₁ levels in pulmonary samples and in BAL aspirates. Material and methods 126 war veterans confirmed for lung disease were assessed and compared with 3 control groups: 1) 64 veterans not exposed to chemical agents, 2) 12 IPF civilian patients and 3) 33 normal persons. Bronchoalveolar lavage was performed using a flexible fiberoptic bronchoscope and the standard manual method. Total protein was measured by Bradford assay and samples corrected with regard to coefficients. Samples were concentrated 15 fold by lyophilization and re-solubilization. Samples were double checked using an ELISA test kit (IBL Co). The Mann-Whitney test was used for the data analysis using commercial software. Results: We detected that significant differences between TGF ₁ levels between the case group and control group1 (p0.001), and control group 3 (p=0.003). No significant differences were found between the case and control group 2 (p=0.57). Conclusion: Inflammation and fibrotic processes in lung tissue of patients exposed to sulfur mustard may be progressive. IFN- maybe useful in these patients.