This study was conducted to investigate the health effects of exposure to silica dust in firebrick manufacturing plants. A cross-sectional study was designed, and the health effects in 526 exposed workers were compared with 164 nonexposed control workers. The medical examination included chest x-rays, pulmonary function tests, and a respiratory symptom questionnaire. Radiological evidence of pneumoconiosis was evident in 6.9% of the exposed firebrick workers, and the prevalence of pneumoconiosis increased with duration of employment. No differences in forced vital capacity were noted between the exposed and control groups; however, in both smokers and nonsmokers of the exposed group, forced expiratory flow in 1 s/forced vital capacity, mean maximal expiratory flow, forced expiratory flow at 50% vital capacity, and forced expiratory flow at 75% vital capacity were significantly lower than in the control group. Pulmonary function decreased as the duration of employment increased. The exposed group experienced significantly more wheezing, compared with the control group. There was evidence of a dose-response relationship between prevalence of pneumoconiosis/pulmonary function defects and estimated dust exposure levels. Pneumoconiosis and pulmonary function defects occurred frequently in workers who participated in the crushing and burning operations, both of which cause exposure to high levels of silica dust. We concluded that exposure to silica dust in workers at firebrick factories leads to radiological changes, pneumoconiosis, and pulmonary function damage.