7. Project Summary We propose to renew the NCI Cancer Epidemiology Training Program. In accordance with NCI instructions limiting support to eight trainees per year, we plan a reduction from the current ten by removing two postdoctoral positions. We leverage the enormously rich academic environment of the Harvard T.H. Chan School of Public Health, together with the Dana-Farber/Harvard Cancer Center, Channing Division of Network Medicine, and a multitude of affiliated institutions within the Boston medical community, as well as with collaborators outside Massachusetts. These resources include the Harvard cohorts (Nurses’ Health Studies I, II, and III, Health Professionals Follow-up Study, Physicians’ Health Study, Women’s Health Study, the VITAL trial, and others). These cohorts have millions of person-years of repeated follow-up for all cancer sites, as well as blood and tissue samples from over 100,000 individuals. The opportunities for cancer research within this environment are virtually limitless. We have brought together outstanding and passionate faculty mentors to provide integrated interdisciplinary experiences and collaborative interactions, a specialized curriculum with core and elective coursework, nondidactic practical career training, individual candidate training plans, and ongoing program evaluation. Cutting-edge didactic training and mentoring will create a new generation of highly skilled and enthusiastic investigators to study factors that influence cancer incidence and survival. A major focus is to take advantage of the multitude of modern ‘omics methods, such as genomics, metabolomics, together with the array of biologic samples, including blood, oral swabs and stool for microbiome, and tumor tissue. The multidisciplinary training will include applying modern epidemiologic and biostatistical methods to analyze such data and develop novel approaches for cancer research. This training program is currently in year 48; we have constantly updated the program, maintaining approaches that work well, initiating new aspects, and taking advantage of new opportunities, and revising our mentor group accordingly. We have vigorously sought to increase the number of mentors and trainees from under-represented minority (URM) groups. We recognize the need for improvement, but are pleased that 20% of the trainees in the first three years are URM individuals and 30% in the final two years. With this renewal application, we initiate a new program to train co-mentors, junior faculty who will be trained to become effective mentors in the future. One constant feature is that we have never had a shortage of outstanding candidates for the program. With continued support, we believe this training program will continue to have a major impact to further the mission of NCI to reduce the burden of cancer through prevention and improved survival.