The cell surfaces under pathological states were observed by a scanning electron microscopy (SEM). Three cases of CLL were T-cell type, e.g. SRBC rosette forming cells, and 3 cases of ALL were null cell type. The surface structure of leukemic cells in CLL was smooth type, or intermediate type, although it was smooth type or a part of the cells had many blebs and ridge-like processes in ALL. A part of peripheral lymphocytes in patients with SLE showed abnormal, irregular shape and had blebs, ridge-like processes. Such abnormal cells were frequently detected in the cases which T-cells were decreased. Leukemic cells in one case of leukemic reticuloendotheliosis (acute type) had very short ridge-like projections. Monocytic leukimic cells had the similar surface structure as normal peripheral monocytes which had ruffled membranes, but their processes were larger or broader. Plasmoid cells in patient with IgG(k) type multiple myeloma had villous surface structure, however that in IgD (λ) type were bullous. This findings suggested that the surface structure was different among immunoglobulin classes which were produced by myeloma cells.