The International Lung Cancer Consortium (ILCCO) is an international group of lung cancer researchers, established in 2004 with the aim of sharing comparable data from ongoing lung cancer case-control and cohort studies. Questionnaire data from a approximately 100,000 case-control pairs, over 1 million cohort participants, and the biological samples from the majority of the subjects would be available. These studies are from different geographical areas and ethnicities. The overall objectives are to achieve greater power, especially for subgroup analyses, reduce duplication of research effort, replicate novel findings, and afford substantial cost savings through large collaborative efforts.