Recently, flow-cytometric analysis has become the most popular type of cell-surface marker examination and it is particularly indispensable in diagnosing hematological disorders such as leukemia. Since diagnosis becomes more reliable using monoclonal antibodies, cell-surface marker analysis contributes greatly to the diagnosis of hematological disorders. In particular in lymphocytic leukemias, immunological classification becomes possible and since this classification has a close relation to pathophysiology and prognosis, it is very useful in diagnosing and treating patients with lymphocytic leukemia. Attempts at quantitative analysis of cell-surface antigens and expected benefits such as improved detail are also described. Additionally the standardization of cell-surface analysis using flow-cytometry is discussed.