Medically underserved populations in the United States continue to experience higher cancer burdens of incidence, mortality, and other cancer-related outcomes. It is imperative to understand how health inequities experienced by diverse population groups may contribute to our increasing unequal cancer burdens and disparate outcomes. The National Cancer Institute convened a diverse group of scientists to discuss research challenges and opportunities for cancer epidemiology in medically underserved and understudied populations. This report summarizes salient issues and discusses five recommendations from the group, including the next steps required to better examine and address cancer burden in the United States among our rapidly increasing diverse and understudied populations. Cancer Epidemiol Biomarkers Prev; 25(4); 573-80. ©2016 AACR SEE ALL ARTICLES IN THIS CEBP FOCUS SECTION, "MULTILEVEL APPROACHES TO ADDRESSING CANCER HEALTH DISPARITIES".