Purpose: Several studies have demonstrated that patients have a poor understanding of prognosis, survival, and effectiveness of chemotherapy, particularly in the setting of advanced cancer. This study examines oncology patients’ understanding of their illness based on accurate reporting of stage at diagnosis and knowledge of cancer status (ie, free of cancer or in remission v active disease). Materials and Methods: Two hundred eight patients with cancer previously treated at our large community-based cancer institute participated in the Consumer-Based Cancer Care Value Index field survey. Electronic medical record documentation of stage at diagnosis and cancer status was compared with patients’ self-reported responses. Concordance of responses and variables influencing discordance were evaluated. Results: In 51.0% of patients, self-reported cancer stage matched the abstracted stage, with the highest concordance in patients with advanced cancer (72%) versus patients with stage I to III disease (36.4% to 61.5%). Unexpectedly, discordance was lower among patients with advanced cancer compared with patients with stage I to III cancer ( P = .0528). Patients who were concordant for cancer stage at diagnosis were significantly more likely to be female ( P = .001), be younger than age 65 years ( P = .01), have an income > $60,000 ( P = .03), and have more education ( P = .02). In 64.4% of patients, self-reported cancer status (ie, free of cancer or in remission v active disease) matched the abstracted status. Nearly 30% of patients were not sure about their status, even when they were free of cancer or in remission. Conclusion: Our findings confirm that more than one quarter of patients with advanced cancer have poor illness understanding and highlight that an even greater number of patients with early stage I to III cancer have poor illness understanding. These observations highlight the need to improve illness understanding for patients across the entire cancer continuum.