Adverse event (AE) reporting is a critical component of all cancer clinical trials, and the National Cancer Institute's Common Terminology Criteria for Adverse Events™ (CTCAE) is the primary system used by clinicians to describe the severity of AEs. The National Cancer Institute's Patient-Reported Outcomes version of the CTCAE (PRO-CTCAE) assesses patient self-reports of symptoms using a Web-based system that can be incorporated into all cancer clinical trials. Oncology clinical trial nurses are responsible for the protection and safety of patients enrolled in cancer trials and, therefore, should develop an understanding of PRO-CTCAE.