Background: In periodical occupational examination, for detection of pulmonary involvement, chest x-ray with ILO classification is used. This protocol is carried out on asbestos workers as well. However, chest x- ray is not valuable for early detection of asbestos related pulmonary changes. This study evaluated HRCT vs. chest x- ray in early detection of asbestos related pulmonary changes. Materials and Methods: This study was performed in November 2002 among "Hajat Chrysotile Asbestos Factory" and mine workers located in Nehbandan-Birjand, Khorasan province. A total of 49 asbestos mine workers with minimal respiratory symptoms were chosen. The level of asbestos in different areas of the factory and mine was measured. All workers were interviewed and underwent clinical examination, chest x-ray and HRCT. Results: The mean value of asbestos in the respiratory field of asbestos exposed workers was about 80 times over the standard limits (39.75 f/ml; TLV= 0.5 f/ml). On chest x-ray based on ILO classification, 3 individuals (6.1%) showed reticulonodular involvement. The most common intensity of involvement was generally I/I in bases of the lungs. HRCT findings demonstrated pulmonary parenchymal involvement in 32 cases (65.3%). In 29 cases, there was no abnormality in chest x-Ray, while it was present in HRCT. In 17 cases both tests were negative. There was no positive chest x-ray in HRCT negative cases. Sensitivity of chest x-ray was 9.5% and specificity was 100%. Conclusion: According to sensitivity, use of chest x-ray as a diagnostic test for evaluation of asbestos related pulmonary diseases does not have enough value for detection of