Dr. Rohan is a cancer epidemiologist who studies the role of genetic/molecular, nutritional, and hormonal factors in the etiology and pathogenesis of a wide range of cancers. Much of his work has focused on breast cancer, in relation to which he has a particular interest in the molecular pathogenesis of breast cancer, where his work focuses on identifying molecular changes in benign breast disease tissue that predispose to the development of subsequent breast cancer. Many of his other studies have involved cohort investigations, mostly within the Women’s Health Initiative cohorts, the Canadian National Breast Screening Study dietary cohort, and more recently within a new cohort that he established, the Canadian Study of Diet, Lifestyle, and Health. He has published many scientific articles on cancer epidemiology, and he has co-edited books on cancer precursors and on cervical cancer.