Cell suspension prepared from the lymph node biopsy of patients with non-Hodgkin’s lymphoma (NHL), metastatic carcinoma (MC) and non-neoplastic lymphadenopathies (NL) were analyzed by the Hemalog D, automated differential counter. The preparation of lymph node cells is described first in this study. The results show that the percentage of large cells (diameter greater than 13.5 μm) stained negatively with peroxidase (LUC, large unstained cells) was remarkably increased in patients with NHL (mean ± SEM = 18.6 ± 3.1 %) and was particularly increased in the subgroup, diffuse histiocytic type (31.1 ± 5.3 %). Patients with MC had a raised percentage of nonspecific esterase-positive cells (9.2 ± 1.4%) compared to patients in the NHL and NL groups. Patients in the NL group had low percentages of both LUC (5.3 ± 0.7%) and nonspecific esterase-positive cells (1.8 ± 0.2%). Quantitation of cells in the lymph node by using the Hemalog D may assist in the diagnosis of lymph node diseases.