The multiple symptoms arising from cancer and its treatment impose significant distress for patients. However, in clinical research, there is no agreed-upon way of assessing and presenting the effects of treatment on multiple symptoms, as either individual scores or a composite score. The ASCPRO (Assessing the Symptoms of Cancer Using Patient-Reported Outcomes) Multisymptom Task Force was established to make recommendations about measuring multiple symptoms as outcomes in cancer clinical trials. The Multisymptom Task Force addressed how to choose the symptoms to be assessed and how multiple individual symptom scores or composite scores of several symptoms might be used as clinical trial outcomes. Consensus was reached on a definition of a multisymptom outcome, the problem of source attribution, and the need for a hypothesis-driven conceptual framework to measure multisymptom outcomes. Validated single-item and multi-item measures currently available or that can be easily generated for oncology use were deemed sufficient for measuring multiple symptoms. The relative value of a composite score versus a set of individual symptom scores was discussed, along with issues in developing and deploying such a composite measure. The results indicated that more research on combining scores of different symptoms is needed. Symptom data should be a required component of cancer clinical trials. Patient-reported symptoms provide a unique patient perspective on treatment benefit and risk that goes beyond clinician-reported adverse events. A representation of changes in multiple symptoms would clarify the impact of treatment and enhance the interpretation of cancer clinical trials for clinicians, patients, and those who make health care policy.