 We have identified 1261 proteins that are thought to be differentially expressed in human cancer. Some of these proteins have already been detected in plasma, while others need further validation. Given sufficient sensitivity, these proteins could potentially be used as biomarkers for early cancer detection and monitoring. Additionally, many of them have been found in studies of tissues and nuclei, suggesting they may also be present in plasma. Only nine of the 1261 proteins have been approved by the Food and Drug Administration, FDA, as tumor-associated antigens. To address this gap between basic research and clinical use of advanced diagnostics, we propose collecting and validating a large number of candidate biomarkers.