A case-control study that included 25,398 cases of lung cancer among Florida residents, first diagnosed in 1981-1983, was conducted to determine if residence in the central Florida phosphate mining region was associated with an increased risk of lung cancer. A twofold increase in lung cancer risk was observed among male nonsmokers who lived in the study area. Risks were elevated for all major lung cancer cell types, with the highest risks observed for small cell carcinoma of the lung. Among cigarette smokers, a slight, but not statistically significant, additional increase in risk was associated with residence in the study area. Among women, no significant elevations in risk were observed for persons who lived in the study area. The greatest increase in risk among women was for small cell carcinomas, but the elevations were not statistically significant.