There is increasing support for the incorporation of patient-reported outcomes (PROs) into clinical trials in cancer. While the need for inclusion of measures of target symptoms in symptom management trials is clear, arguments can also be made for measurement of a broader range of symptoms, for evaluation of symptom burden, and for evaluation of health-related quality of life (HRQOL) in these trials. What is key to their inclusion is a priori selection of instruments, provision of a theoretic basis for inclusion of instruments, and a clearly described plan of analysis. The federal Food and Drug Administration (FDA) has provided guidance regarding the use of PROs (symptom and HRQOL measures) to support treatment benefit claims in product labeling. Moving forward, research is needed to address methodological issues raised by the FDA and to increase understanding of relationships among symptoms, symptom clusters, HRQOL, and other outcome measures.