European epidemiological studies on ambient air pollution and cancer published before December 2006 are reviewed, with focus on five analytic studies providing data on the association between various measures of particulate matter (PM) and lung cancer. A case-control study of 755 men who died from lung cancer in Trieste, Italy, reported that, compared with less than 0.18 g/m/day of deposition of particulate, the relative risk (RR) was 1.1 [95% confidence interval (CI): 0.8-1.5] for 0.18-0.30 and 1.4 (95% CI: 1.1-1.8) for more than 0.30 g/m/day. In the Netherlands Cohort Study on Diet and Cancer with 60 deaths from lung cancer, the RR was 1.06 (95% CI: 0.43-2.63) for an increase of 10 mug/m in black smoke. In the French Pollution Atmospherique et Affections Respiratoires Chroniques study cohort based on 178 deaths from lung cancer, the RR associated with an increase in exposure to 10 mug/m of total suspended particulate was 0.97 (95% CI: 0.94-1.01). A nested case-control study within the European Prospective Investigation on Cancer and Nutrition included 113 nonsmokers or exsmokers diagnosed with lung cancer and 312 controls. The RRs were 0.91 (95% CI: 0.70-1.18) for an increase in PM with diameter </=10 mum (PM10) of 10 mug/m, and 0.98 (95% CI: 0.66-1.45) for exposure over 27 mug/m compared with less than 27 mug/m. In a Norwegian record linkage study, based on 1453 lung cancer deaths, no significant excess risk was found for men, and a modest association was observed for women. European studies of PM exposure and lung cancer do not show a clear association, but uncertainties remain for the measurement of exposure and latency.