In contrast to clinical biopsies, where tissue is collected to inform patient care, research biopsies are performed for scientific purposes to potentially enhance understanding of the biologic bases of cancer and drug action, thereby improving diagnosis and treatment, but they may offer no direct benefit to participants and have known risks. The widespread use of research biopsies that do not have the potential to directly benefit participants has come under scrutiny, with critics raising ethical concerns related to the adequacy of participant protections, informed consent, and participant understanding of the risks and benefits, as well as the scientific impact of research biopsies on drug development and treatment. This manuscript presents the American Society of Clinical Oncology's (ASCO's) ethical framework for incorporation of research biopsies in trials. The framework provides guidance on the circumstances to include optional and mandatory biopsies, as well as provides recommendations to stakeholders on necessary steps for improving the conduct of research biopsies overall.