Background: Immunophenotyping of haematological malignancies is one of the most extended and useful clinical applications of flow cytometry.In this regard, flow cytometry is currently used in establishing the diagnosis, the prognostic classification and the evaluation of effectiveness of treatment of most haematological malignancies, including both leukemias and lymphomas.Over the past decade, several molecular techniques have brought new insights into the prognostic classification and monitoring of residual disease after therapy in many different clonal haematological disorders.However, molecular techniques have several major disadvantages.Among other, they are time consuming, they have a limited applicability and they provide information about samples, without focusing on cell populations within a sample, unless preceding purification steps are performed.These limitations can be overcome by innovations in flow cytometry immunophenotyping, because this technology uniquely fulfills the requirements for high speed, accurate focusing on the malignant cell population, at the same time it is broadly applicable at diagnosis and follow-up for the detection of surface bound, intracellular and even soluble proteins, as immunophenotyping targets with well-defined antibodies.