The Cancer and Leukemia Group B (CALGB) Leukemia Correlative Sciences Program has worked to attain a highly successful integration of correlative laboratory studies into the design and implementation of CALGB leukemia trials. Dr. Michael A. Caligiuri assumed leadership of the CALGB Leukemia Correlative Science Committee (LCSC) in August of 1999 following 18 years of Committee leadership by Dr. Clara Bloomfield. The LCSC has been restructured and refocused entirely on leukemia, moving evermore into the molecular age of diagnostics, pathogenesis, and treatment. The goal is to use cytogenetics, immunology, and molecular biology to better understand the heterogeneity of leukemia with regard to diagnosis, prognosis, and ultimately treatment. In this competitive renewal application, we have assembled three Cores (Cytogenetics, Banking, and Administration) and six Projects, each of which is utilizing materials collected from patients treated on CALGB leukemia treatment protocols in order to address a scientific question and correlate it with disease outcome. Having set into motion a paradigm for stratification of leukemia treatment based on risk of relapse during this last funding cycle, the current CALGB Leukemia Correlative Science application will attempt to dissect out additional leukemia patients that can be predicted to do well or do poorly in response to standard or novel therapies, and to then work with the CALGB Leukemia disease committee to stratify their treatment based on risk. In this way, we hope to significantly impact on the cure rate of leukemia over the next six years of funding.