Exposure to environmental tobacco smoke (ETS) is an established cause of lung cancer, ischaemic heart disease and chronic respiratory disease in adults and of asthma in children. A meta-analysis of 48 risk estimates from 39 published studies in non smokers gave a relative risk of 1.24 (95% Confidence Interval: 1.15-1.34), 1.14 (95% CI: 0.98-1.33) and 1.15 (95% CI: 0.92-1.43) for spousal, working environment and childhood ETS exposures. Misclassification of active smokers, exposure to ETS in reference groups, dietary confounding and publication bias have little effect on the association with spousal exposure. Estimates of the number of lung cancer deaths attributable to ETS from spousal exposure gave 1146 and 200 yearly deaths in the European Union (EU) and Italy respectively. Review of the available evidence confirms that exposure to ETS increases the risk for lung cancer and other diseases and is an important public health problem in the EU and Italy.