In order to investigate the size variation of neoplastic cells from lymph nodes of 19 patients with B-cell non-Hodgkin's lymphomas (B-NHL), we have carried out the two-dimensional analysis by flow cytometry using the parameters of the forward light scatter (FLS) and the fluorescence intensity of surface immunoglobulin light chain (sIgL). Neoplastic B cells were identified as having the homogeneous characters of both FLS and sIgL (kappa or lambda) in comparison of normal B cells with the heterogeneity of counterpart sIgL (lambda or kappa). Then the size variation of neoplastic B cells was analyzed by regarding CD3+ T cells to a control scale. Consequently, the present procedures disclosed that B-NHL cases could be divided into five patterns from the view-point of the cell size and distribution. These results almost coincided with the cell types determined by the pathological diagnosis. Furthermore, it was also found that our data made it possible to classify small cleaved cell or large cell lymphomas into subtypes. The two-dimensional analysis by using the parameters of FLS and sIgL would be clinically useful for the rapid diagnosis of B-NHL and its malignant grade in addition to supporting pathological findings.