Thirteen monoclonal antibodies submitted to the Third Workshop on Erythrocyte Antigens from the panel "non-specific erythrocyte antigens" were tested for their reactivity with different types of cells. Most of them were defined as specific for adhesion antigens. The CD 44 antibodies 2D3-1, 2D3-2, 2D3-3 and 2D3-4 reacted as expected for CD 44 except their negative reactivity with the myeloid cell line HL 60 and B-cell line Raji. The CD 47 antibodies 2D3-5 and 2D3-6 reacted specific. Only with Raji and T-cell line MOLT 4 the CD 58 antibodies 2D3-7 and 2D3-8 showed reactivity as expected which indicates that they are "CD 58 related". The CD 99 antibody 2D3-9 shows similar results as expected for a CD 99 specific antibody except its high reactivity against Raji. From the RBC-related antibodies 2D3-11 and 2D3-12 the latter becomes completely negative with trypsin treated erythrocytes. The antibody is negative on normal peripheral blood lymphocytes but reacts with transformed cell lines like Raji and MOLT 4. With a view to their reactivity to the cells tested at least 2D3-13 of the Rh-related antibodies seems to be similar to CD 47 antibodies.