B-cell lymphoproliferative disorders (B-CLPD) are a biologically heterogeneous group of malignant diseases characterized by accumulation of mature B lymphocytes in the bone marrow, peripheral blood and lymphoid tissues. B-CLPD is now mostly diagnosed by flow cytometric immunophenotyping. We aimed to throw light on the expression of CD160 in B – chronic lymphocytic leukemia and demonstrate if it can differentiate B – CLL from other causes of absolute lymphocytosis and to correlate its expression with laboratory findings and immunophenotyping (CD markers). This study included 20 patients recently diagnosed as chronic lymphocytic leukemia who attended medical oncology department of Zagazig University hospitals between April 2017 and April 2018 and 20 cases with other causes of absolute lymphocytosis from outpatient clinic. All studied patients were subjected to full history taking, complete clinical examination and laboratory investigations including CBC Leishman - stained peripheral blood smears for differential leucocytic count, liver functions, kidney functions, serum LDH level, Hepatitis C virus antibody, Hepatitis B surface antigen, HIV Ag, Ab and immunophenotyping. Measuring expression of CD160 on B cell lymphocytes in combination with CD19 in both patients and control groups. There were no significant correlations between CD160% and hematological findings, LDH, liver and kidney function findings. There was significant positive correlation between CD160% and CD23% and CD5%, while there was no significant correlation between CD160 and other flow markers expression in CLL.