The different methods proposed for preparation of B lymphocyte suspensions are not always simple, rapid and reliable. Presence of monocytes in the B cell suspension makes difficult HLA-DQ typing. For these reasons we propose a method using monoclonal antibodies (McAb) and complement to lyse the non B cells. Mononuclear cells, isolated from peripheral blood by Ficoll-Hypaque, are suspended in a mixture of anti-CD2, CD3, CD11b (OKM1 recognizing monocytes and granulocytes) McAb. This method of preparation of B cell suspension is rapid and provide better typing reactions than did the suspensions prepared by depletion of sheep red blood cell rosetting cells.