NCI is collaborating with the Maria Skłodowska-Curie Memorial Cancer Center and Institute of Oncology in Warsaw and the Nofer Institute of Occupational Medicine in Łódź on a large population-based study to assess the role of environmental and genetic factors on breast, ovarian, and endometrial cancer risks. This is a complex study that combines detailed exposure assessment (i.e., detailed questionnaire, physical activity monitors, and anthropometric measurements) with collection of biological specimens (i.e., blood, buccal cells, urine, paraffin-embedded tissue, and frozen tissue samples) from 2,386 breast, 347 ovarian, and 555 endometrial cancer cases, and about 2,500 shared controls. Numerous reports from this study have been published on the major areas of interest, which include evaluation of genetic susceptibility factors, other risk factors such as physical activity, anthropometry, active and passive smoking, and occupational exposures. The study is using tissue microarray technology for high-throughput molecular characterization of tumor and non-neoplastic tissue, and investigators are extracting nucleic acids from tissue cores to create a resource for DNA-based studies. NCI investigators are also collecting five-year follow-up data from breast cancer cases participating in the study in order to evaluate determinants of survival and recurrence, including tumor characteristics and common genetic variation.