Symptom burden is certainly not a new concept in the literature on disease and treatment, but recent developments in our understanding of how to measure symptoms and their impact make it possible to cast symptom burden as a reasonable summary measure of both disease-and treatment-outcome status. We discuss the use of symptom burden as an alternative to quality-of-life measures or as a supplement to these measures. We examine the potential responsiveness and relative ease of interpretation of a symptom-burden outcome. We review studies of the prevalence and negative impact of multiple symptoms on health outcomes among cancer patients. By way of example, we illustrate the potential utility of a measure of symptom burden in the epidemiologic studies of multiple symptoms as well as an outcome measure in clinical studies. Finally, we discuss potential research challenges and offer recommendations on future research directions.