cytometric immunophenotyping has evolved from two-parameter quantitative measurement of peripheral blood lymphocytes to five-or more parameter qualitative evaluation of bone marrow for hematopathology.Leukemia/lymphoma immunophenotyping represent an important addition to histomorphology in the diagnosis,classification and monitoring of hematolymphoid neoplasms.The complexity of five-or more parameter analyses and the interpretation of the data rely on standardization and validation of the instrument,the reagent and the procedure.In addition,clinical flow cytometry laboratories in U.S.are required to document proficiency testing,sample preparation,method accuracy,specificity,sensitivity and precision.CLSI and the U.S.-Canadian Consensus Conference have provided recommendations,but each laboratory is responsible for validating its own qualitative and quantitative procedures.This paper introduces the procedures for quality control of all levels of the operation in a clinical flow cytometry laboratory in USA. cytometric immunophenotyping has evolved from two-parameter quantitative measurement of peripheral blood lymphocytes to five-or more parameter qualitative evaluation of bone marrow for hematopathology. Leukemia / lymphoma immunophenotyping represent an important addition to histomorphology in the diagnosis, classification and monitoring of hematolymphoid neoplasms. complexity of five-or more parameter analyzes and the interpretation of the data rely on standardization and validation of the instrument, the reagent and the procedure. In addition, clinical flow cytometry laboratories in USare required to document proficiency testing, sample preparation, method accuracy , specificity, sensitivity and precision. CLSI and the US-Canadian Consensus Conference have provided recommendations, but each laboratory is responsible for validating its own qualitative and quantitative procedures. This paper introduces the procedures for quality control of all levels of the operation in a clinical flow cytometr y laboratory in USA.