Cancer fatigue has been defined and described as an important problem. However, few studies have assessed the relative importance of fatigue compared with other patient symptoms and concerns. To explore this issue, the authors surveyed 534 patients and 91 physician experts from 5 NCCN member institutions and community support agencies. Specifically, they asked patients with advanced bladder, brain, breast, colorectal, head and neck, hepatobiliary/pancreatic, kidney, lung, ovarian, or prostate cancer or lymphoma about their “most important symptoms or concerns to monitor.” Across the entire sample, and individually for patients with 9 cancer types, fatigue emerged as the top-ranked symptom. Fatigue was also ranked most important among patients with 10 of 11 cancer types when asked to rank lists of common concerns. Patient fatigue ratings were most strongly associated with malaise (r = 0.50) and difficulties with activities of daily living, pain, and quality of life. Expert ratings of how much fatigue is attributable to disease versus treatment mostly suggested that both play an important role, with disease-related factors predominant in hepatobiliary and lung cancer, and treatment-related factors playing a stronger role in head and neck cancer.