The overarching goal of COGS is to identify individuals with an increased risk of breast, ovary and prostate cancer. Furthermore, we will evaluate the effect of inherited genetic variation on tumour characteristics and clinical outcome. We will do this through quantifying the role of genetic and environmental/lifestyle risk in the largest data set ever generated. In all, we will include over 200,000 individuals in the COGS project. We will use detailed knowledge of the architecture of genetic susceptibility and interactions with environmental/lifestyle factors which will result in much more accurate individual risk prediction and improved intervention strategies. We are taking advantage of a unique possibility by incorporating seven existing consortia into one large project – COGS. Members of these consortia have collaborated successfully over the past years and results have been presented in world leading scientific journals such as Nature, Nature Genetics and Journal of the National Cancer Institute. These papers reflect that collaboration has been ongoing and that is has so far been very successful. We will also build on an existing European Commission project, TRANSBIG, thus adding value to already spent money. Results generated through COGS will lead to an improved understanding of the biological processes that underlie carcinogenesis, that in turn could guide new therapeutic strategies. Results will also lead to the development of new tests for risk prediction for breast, ovarian and prostate cancer.