Inhalation of crystalline silica has long been associated with lung disease. The rate of disease progression i.e. acute, accelerated or chronic silicosis seems to depend on the rate of deposition as well as the total burden of crystalline silica in the lung. Despite intensive studies, yet little is known about the crucial cellular and molecular mechanisms that initiate and propagate the process of inflammation and scarring. Recent studies have indicated a role of increased oxidant stress in these patients. In the present study, oxidant stress was assessed by measurment of lipid peroxides (LPER) as a resultant of free radical injury as well as the antioxidants, superoxide dismutase (SOD), catalase, ceruloplasmin (CER) and vitamin C in 50 male persons, stratified according to their duration of exposure. Their ages ranged from 24 to 42 years (mean ± S.D. 33.01 ± 1.72 years). Forty male persons are included who are age matchable to patients are presenting controls. For each participant spirometry was done to measure pulmonary function tests. Blood samples were withdrawn by venipuncture, plasma were separated and used for determination of LPER, SOM, CER and vitamin C and RBCs for catalase. The study revealed marked degree of enhanced oxidant stress in patients exposed to silica as manifested by significant increase in LPER and significant decrease in plasma SOD and RBCs catalase (P<0.001 for each) in exposed patients compared to controls. Meanwhile, plasma levels of vitamin C and CER are significantly increased (P<0.001 for each) compared to controls. The levels of SOD and catalase were significantly decreased with prolonged duration of exposure while the levels of CER, vitamin C and LPER were significantly increased (P<0.001 for each). A highly significant correlation was observed between LPER and age as well as duration of exposure. The present data clearly indicate the role of oxidant stress in silica induced lung injury. However, much clinical follow up of workers exposed to this hazardous material is required. To decrease the oxidant stress, antioxidant measures should be considered.