The goal of the proposed research is to examine how the independent and combined effects of childhood adiposity (assessed by body mass index [BMI]; kg/m2) height, change in BMI and height, and pubertal timing from the ages of 7 to 13 years are associated with the risk of cancer incidence in adulthood. Greater body size (adipose tissue and different types of lean tissue) reflecting past or ongoing growth may increase the risk of cancer in individuals as greater numbers of proliferating cells increase the risk that mutations leading to the subsequent development of cancer occur. As childhood is a period of growth, it is plausible that it is of particular relevance for the early establishment of the risk of cancer.Data from the Copenhagen School Health Records Register, which is based on a population of schoolchildren born between 1930-1983 and contains computerised weight and height measurements on >350.000 boys and girls in the capital city of Denmark, as well as data from other cohorts will be used. Survival analysis techniques and the newly developed Dynamic Path Analysis model will be used to examine how body size (BMI and height) at each age from 7 to 13 years as well as change in body size during this period is associated with the risk of multiple forms of cancer in adulthood with a simultaneous exploration of the effects of birth weight and pubertal timing. Additionally, potential effects of childhood and adult health and social circumstances will be investigated in sub-cohorts with this information available.Results from this research will demonstrate if childhood is a critical period for the establishment of the risk for cancer in adulthood and will lead into mechanistic explorations of the associations at the biological level, investigations into associations between childhood body size and mortality and contribute to developing improved definitions of childhood overweight and obesity that are based upon long-term health outcomes.