A major limitation in the treatment of malignant disorders is the accurate and sensitive detection of minimal residual disease. It is clear that routine radiographic and pathologic studies are extremely important, however, lacking in sensitivity. Clearly, the goal of minimal residual disease detection is to make individual treatment decisions such that those patients who require more aggressive approaches are treated promptly and to avoid toxic and expensive treatments for those patients who do not require them. To reach this goal two milestones are required. The first is to develop and standardize sensitive and specific tools to detect minimal residual disease. The second is to determine whether these tools in fact predict clinical outcome. This review is divided into two parts. In the first section, recent advances in the detection of minimal residual disease will be discussed. This will be followed by studies reported in the past year that have attempted to determine whether those assays are reliable and predict clinically relevant endpoints.