Current tumor markers are limited in their clinical utilities. They are only useful for monitoring cancer patients during treatment and for detecting recurrence. Because of the lack of specificity and sensitivity, currently used tumor markers are not recommended for screening or diagnosis. Therefore, new tumor markers are being sought to improve the sensitivity for cancer detection and to improve the specificity for diagnosis. In this chapter we introduce several new tumor markers to complement currently used tumor markers. These new tumor markers may provide specificity and improved sensitivity for cancer management. Recently the importance of using tumor markers for target therapy, prognosis, and early detection has been emphasized (1). Therefore, there is a need to discover new circulating tumor markers for use in these areas. Introduced in this chapter are several new tumor markers that appear to have improved clinical utilities. In addition, a new group of circulating tumor markers are also described in this chapter relating to the signal transduction pathway, cell cycle, apoptosis, angiogenesis, and adhesion. This addition is largely owing to the recent change of emphasis on tumor markers. Instead of stressing diagnosis, monitoring and early detection of recurrence, the emphasis is placed at early tumor detection, prognosis, and target therapy. Note that these new tumor markers are also detectable in blood circulation. Because their appearance in the circulation are associated with various stages of growth regulation of cells, their detection could be correlated with prognosis and to be detectable in early neoplasm, and to be identifiable as target for target therapy. As will be shown below, these new markers involve not only oncoproteins and mutated suppressor proteins but also enzymes and various factors. Although not yet fully verified, these new tumor markers described here should greatly improve the use of circulating tumor markers in cancer management.