INTRODUCTION: Aspects of a personal cancer history can have implications for future decisions regarding screening, diagnosis, and treatment. Clinicians must sometimes rely on patients' self-report of their medical history. This study assessed knowledge of details of cancer diagnosis and treatment among breast and colorectal cancer survivors. METHODS: Written surveys were completed by 480 breast cancer survivors and 366 colorectal cancer survivors diagnosed between 1999 and 2008 at a large cancer center in the Minneapolis, MN, area (81% response rate). Responses were compared with cancer registry and medical records. RESULTS: Forty percent of breast cancer survivors and 65% of colorectal cancer survivors were unable to identify their stage of disease. Seven percent of breast cancer survivors and 21% of colorectal cancer survivors in whom regional nodes were examined did not know whether they had positive nodes. Accuracy of knowledge of estrogen and progesterone status among breast cancer survivors was 58% and 39%, respectively. Of breast cancer survivors treated with doxorubicin, 43% correctly identified it as a drug they had received. Their accuracy of identification of receipt of tamoxifen or specific aromatase inhibitors was >90%. Of colorectal cancer survivors treated with oxaliplatin, 52% correctly identified it as a drug they had received. Accuracy on many items decreased with patient age. CONCLUSIONS: This study identifies several gaps in adult cancer survivors' knowledge of details of their diagnosis and treatment that have implications for follow-up care. IMPLICATIONS FOR CANCER SURVIVORS: Provision of written treatment summaries to cancer survivors could help them obtain appropriate patient-centered long-term follow-up care.