Background: The role of crystalline silica dust as a possible cause of lung cancer has been controversial. Relatively few large community- based studies have been conducted to investigate the lung cancer risk from exposure to silica at low levels, taking into account potential confounding factors. Methods: Detailed lifestyle and occupational information were collected from 2852 newly diagnosed cases of lung cancer and 3104 controls between 1998 and 2002 in 7 European countries. For each job held, local experts assessed the probability, intensity, and duration of silica exposure. Results: Occupational exposure to crystalline silica was associated with an increased risk of lung cancer (odds ratio = 1.37; 95% confidence interval = 1.14 -1.65). This risk was most apparent for the upper tertile of cumulative exposure (OR = 2.08; 95% CI = 1.49 -2.90; P for trend <.0001), duration of exposure (1.73; 1.26- 2.39; P for trend < 0.0001) and weighted duration of exposure (1.88; 1.35-2.61; P for trend <.0001). We did not observe any interaction beyond a multiplicative model between tobacco smoking and silica exposure. Conclusions: Our results support the hypothesis that silica is an important risk factor for lung cancer. This risk could not be explained by exposure to other occupational carcinogens or smoking, and it was present for the main histologic types of lung cancer, different sources of silica exposure, and different industrial settings.