The frequency of HLA class-I and class-II antigens was investigated in 32 Iranian patients with B-cell chronic lymphocytic leukemia (B-CLL), using the microlymphocytotoxicity method. A significant increase in the HLA-B13 (P<0.01) and DR53 (P < 0.05) and a significant negative association with the A11 (P < 0.05), B35 (P < 0. 05), Cw3 (P < 0.05), and DR1 (P < 0.02) antigens were observed in these patients, compared to the control normal population. These results suggest involvement of some HLA antigens in the multifactorial process of predisposition to B-CLL.