The purpose of this article is to analyze the concept of symptom clusters and to discuss its application to cancer nursing to promote communication and enhance scientific knowledge. Rodgers' evolutionary method of concept analysis served as the framework for reviewing literature from psychology/psychiatry, general medicine, and nursing. Attributes of symptom clusters were relationships of symptoms and relationships of clusters, concurrence, underlying dimensions, stability, and common etiology. The major antecedent was the presence of 2 or more symptoms. Consequences were poorer physical health status, interference with activities of daily living, emotional distress, and increased financial burden. A symptom cluster is defined as consisting of 2 or more symptoms that are related to each other and that occur together. Symptom clusters are composed of stable groups of symptoms, are relatively independent of other clusters, and may reveal specific underlying dimensions of symptoms. Relationships among symptoms within a cluster should be stronger than relationships among symptoms across different clusters. Symptoms in a cluster may or may not share the same etiology. Symptom should be broadened to include both subjective (self-reported) symptoms and objective (observed) signs. Implications for researchers include the need to use a clear definition, determine the optimal methods of identifying etiology and nature of symptom clusters in various populations, assess the clinical utility of symptom clusters, and test interventions. Implications for practitioners include the need to comprehensively assess symptoms over the entire cancer trajectory, select interventions that target single and multiple symptoms, and evaluate outcomes that include quality of life and economic variables.