This issue of Clinics in Laboratory Medicine, edited by David M. Dorfman, will cover Flow Cytometry. Topics covered in this issue include: Flow cytometric evaluation of primary immunodeficiencies; Flow cytometry of B cell neoplasms; Flow cytometry of T cell neoplasms; Flow cytometry of acute myeloid leukemias; AML minimal residual disease (MRD) assessment by flow cytometric analysis; Acute lymphoblastic leukemia minimal residual disease (MRD) assessment by flow cytometric analysis; Flow cytometric assessment of myelodysplasia and myeloproliferative neoplasms; Flow cytometry of plasma cell neoplasms, including MRD testing; Paroxysmal nocturnal hemoglobinuria (PNH) assessment by flow cytometric analysis; Mast cell disease assessment by flow cytometric analysis; Flow cytometry in pediatric hematopathology; Clinical applications of mass cytometry; Automated analysis of clinical flow cytometry data; and Cost-effective flow cytometric testing strategies.