Context: The Functional Assessment of Cancer Therapy-Head and Neck is a well-validated assessment of quality of life used with patients diagnosed with head and neck cancers (HCNs). The present study is an attempt to evaluate and modify this instrument as necessary in light of the recent regulatory guidelines from the Food and Drug Administration on the use of patient-reported outcomes in clinical trials. Objectives: Overall, the goal was to identify patients' highest priority cancer symptoms, compare these symptoms with those suggested by oncology experts, and construct a brief symptom index to assess these symptoms and categorize them as treatment-related, disease-related, or related to general function and well-being. Methods: Patients (N = 49) with advanced (Stages III and IV) HCNs were recruited from participating National Comprehensive Cancer Network institutions and community cancer support organizations in the Chicago area. Patients completed open-ended interviews and symptom checklists. Participating oncology physician experts also rated symptoms. Content validity was obtained by evaluating results alongside items in the Functional Assessment of Chronic Illness Therapy system. Eleven oncologists categorized symptoms in terms of importance and also whether the symptoms were primarily related to disease, treatment, or functional well-being. Results: HCN-related symptoms endorsed as high priority by both patients and oncology experts were selected for the new National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy-Head and Neck Cancer Symptom Index-22. The final version includes 22 items, which are broken down into disease-related symptoms, treatment side effects, or general function and well-being. The new scale has acceptable internal consistency (Cronbach's coefficient alpha = 0.86), content validity for use in chemotherapy trials of patients with advanced disease, and concurrent validity as demonstrated by moderate-to-strong correlations with the existing Functional Assessment of Chronic Illness Therapy measure. Conclusion: The National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy-Head and Neck Cancer Symptom Index-22 adequately reflects symptom and side effect concerns of advanced HCN patients as well as oncology physicians. This instrument can be used to evaluate the most important disease-related symptoms, treatment side effects, and function/well-being in patients with advanced HCNs in clinical practice and research.