This laboratory processes about 1300 multiparametric studies per year for leukemias and lymphomas. Residents review the principles of flow cytometry instrumentation and observe and assist sample processing and staining. They learn the importance of proper gating, techniques for focusing on populations of interest, and the importance of isotype controls. Residents learn to recognize characteristic diagnostic staining patterns in a wide spectrum of leukemias and lymphomas, and they correlate these results with the smear and biopsy morphology of corresponding peripheral blood, marrow and solid tissue sample. Residents also learn the specialized role of flow cytometric immunophenotypic in monitoring HIV progression by CD4/CD8 counts, for CD34 enumeration in stem cell harvesting, and for DNA ploidy analysis in solid tumors. Residents participate in all signout sessions during this week as well as the rest of the month of their Molecular Diagnostics Rotation. They are responsible for correlating the flow data with morphologic data and suggesting an interpretation.