The SYNERGY project was established in 2007 to provide a scientific basis for recognition of lung cancer as an occupational disease in workers exposed to more than one lung carcinogen. It represents the largest database of case-control studies on lung cancer with complete life course information on occupation and tobacco smoking. Data from 19 370 lung cancer cases and 23 674 controls are available from 16 case-control studies conducted between 1985 and 2010. Cases were recruited from hospitals or cancer registries, and in most studies eligible if: 1)<75 years; 2) resident for at least one year and 3) confirmed diagnosis of lung cancer by histology or cytology. Controls were recruited from the general population (81%) or hospitals (19%), and were individually or frequency matched to cases by sex and age. Information was predominantly collected by interviews with the study participants themselves, though next-of-kin respondents were accepted in five of the studies if subjects were unavailable (9.1% of cases, 6.6% of controls). Ethical approvals for the original studies were obtained in each country and for the SYNERGY project from the IARC Ethics Committee. The database comprises around 14% never smokers, whereof 822 cases. Women represent around 20% or the study population. The strengths of SYNERGY includes bringing together epidemiologists and exposure assessment experts from around the world to advance occupational cancer epidemiology, 2) power to study small risks, 3) providing quantitative exposure estimates for population-based case-control studies, and 4) allowing sub-group analyses, e.g. by gender, histology and smoking status.