The relationship between silica (14808607) exposure and lung cancer was discussed, based on experimental evidence in laboratory animals and epidemiological data from occupational studies. Cancer risk assessments for silica and regulations on work and ambient exposures were considered. The evidence for silica exposure as a cause of lung cancer was evaluated using standard criteria. Data from rat studies indicated that silica exposure caused respiratory tumors without prior initiation by a known agent. Worker studies on the link between silica exposure and pulmonary cancer were grouped into five categories: general silica exposure, mining and quarrying, granite industry, ceramics and glass industry, and foundry industry. Case reports, descriptive studies, and epidemiological data were presented for all the categories of human exposure to silica except general exposure. In all cases, the standardized mortality ratios (SMRs) among workers in the exposed groups were significantly higher when compared to the control SMRs. Autopsy and epidemiological study results from studies of workers' risk after diagnosis with silicosis were presented. The lack of positive association in some of the autopsy studies were attributed to biases such as age, smoking, and other pulmonary conditions. Several sources of bias which affected two of the 24 reviewed epidemiological studies were attributed to detection bias, exposure to other agents, and smoking. Cancer risk assessments were based on experimental animal data; possible methods to decrease the uncertainty level associated with such extrapolations included the use of human data. The determination of the relationship between silica exposure and lung cancer required the comparison between exposure and silicosis on the following criteria: strong relative risk, consistent results, dose response gradients, controlled confounding, reliable exposure data, biological specificity, and temporal cogency. The author concludes that chronic silicosis predisposes to a higher risk of lung cancer, and that such a risk results from high silica exposure and/or to the fibrotic process.