Leukemia is the most commonly occurring cancer among children. Despite improved assessment of parental and early life exposures, the relative rarity of the disease makes the study of the environmental and genetic risk factors challenging. A group of independent, international researchers established the Childhood Leukemia International Consortium (CLIC) to overcome the limitations of individual, smaller studies, and support the study of causal factors in the etiology of childhood leukemia. The annual meetings of the CLIC consortium provide an important opportunity for CLIC investigators, as well as other interested parties, to develop and discuss collaborative analyses and future projects. These annual in person meetings also provide the opportunity to build trust, respect and confidence among researchers from different countries;to provide guidance and advice to researchers planning new studies;and to provide a forum for discussion, development, and pursuit of new research directions. Specifically, the 2011 CLIC Annual Meeting will provide attendees with the opportunities to: 1) Discuss novel scientific hypotheses, cutting edge techniques in genetic studies, methodologic issues in pooled analyses, and other topics of emerging interest, 2) Conduct working sessions for all members pursuing collaborative studies and develop proposals for pooled analyses from international epidemiologic studies of childhood leukemia; 3) Develop needed data dictionaries and classification systems and beta test the new web-based interactive CLIC centralized data repository;and, 4) Coordinate research activities with the childhood leukemia study being conducted by the International Childhood Cancer Cohort Consortium (I4C). Public Health Relevance: Although leukemia is the most frequent cancer occurring among children, its relative rarity makes the study of the environmental and genetic risk factors challenging. The Childhood Leukemia International Consortium (CLIC) consists of a group of independent and international researchers who are committed to pooling resources and data with the ultimate goal of understanding the causes of childhood leukemia and identifying targets for intervention and prevention. The annual meetings of the CLIC consortium provides an opportunity for CLIC investigators, as well as other interested parties, to develop collaborative projects and data analyses;build trust, respect and confidence among researchers from different countries;provide guidance and advice to researchers planning new studies;and provide a forum for discussion, development, and pursuit of new research directions.