Lymphoid cells isolated from lymph nodes, spleen and the peripheral blood were examined using the rosette test with sheep erythrocytes (E), immunofluorescent staining of the surface immunoglobulins (Smlg) and the combined test (Smlg+E). The studies were performed on 48 patients with untreated non-Hodgkin lymphoma, 14 Hodgkin patients, 5 patients with lymphadenitis and on 132 controls. In the control group the following percentages of B-T lymphocytes were obtained: blood (n=100): T-68 ± 9, B-20 ± 6, 0-11 ± 7, BT-1 + 1, lymph nodes (n=24): T-62 ± 13, B-19 ± 11, 0-18 ± 8, BT-1 ± 1, spleens (n=8): T-45 ± 9, B-33 ± 9, 0-23 ± 7, BT-1 ± 1. In non-Hodgkin lymphoma lymph nodes a statistically significant increase of B and ‘null’ cells was noted in comparison to controls and to the Hodgkin lymphoma group. The characteristics of the Hodgkin nodes did not differ significantly from controls. After arranging the non-Hodgkin lymphomas according to the Kiel classification it was observed that in the low-grade malignant lymphomas subtype most often an immunological ‘B type’ and ‘mixed B/0’ type was present whereas the high-grade malignant lymphoma group showed a distinct majority of ‘null’ cells. It was concluded that the surface markers studied allow a differentiation in most cases between the non-Hodgkin lymphomas and other disorders of the lymphoid system. They are not sufficient to distinguish the subtypes of non-Hodgkin lymphomas but do give interesting information about the more exact nature of the disorder.