We performed lymphocyte transformation tests using 14 different mitogens and antigens, determined T-cell- and T-cell subpopulation counts (CD3, CD4, CD8), the CD4/8 ratio, granulocyte chemotaxis and granulocyte adherence in 88 healthy controls, 8 patients with immunoblastoma (IB) and 6 patients with lymphoblastoma (LB). Using cluster and discrimination analyses (F-test; t-test) according to the programs of the UCLA (BMDP2N) the control group (n = 88) could be divided into 3 groups with significantly different lymphocyte responses to mitogenic and antigenic stimulation (21 high-, 18 medium, and 49 low responders). Comparing the lymphocyte reactivity of IB and LB patients to these immunofunctional different clusters we found a complete accordance of the lymphoma patients to the healthy low responder group.