A Symptom Cluster Concept and Its Importance The cancer patients experience multiple symptoms, which are difficult to manage, during illness, treatment period, and after the treatment and at terminal stage. Understanding of the symptoms, their etiologies, the relationships between symptoms and factors are important for providing effective symptom management and improving the quality of life. When three or more concurrent symptoms are related to each other, they are called a symptom cluster (e.g., pain, fatigue, sleep disturbances). The concurrent symptoms form the symptom clusters (e.g., nausea, vomiting, poor appetite). During the cancer treatment, the symptom groups affect negatively the functional and emotional status and quality of life, and thus they cause challenges in the care and symptom management of the cancer patients. The management of symptom clusters, which occur cause of disease or treatment, should focus not only on one symptom but on all symptoms that are experienced concurrently. Investigations about symptom clusters and care specific to symptom clusters will contribute positively to reducing the use of polypharmasy and systemic toxicities, and decrease the negative effects of symptom clusters .