Cellular immunity was evaluated in 15 untreated patients with Hodgkin's disease before and about 10 days after splenectomy. Skin test-reactivity was not affected by the operation. The number of lymphocytes was moderately increased in patients with pathologic stage I and II disease. The relative proportion of E-binding lymphocytes in the peripheral blood diminished significantly (p = .001) in patients with splenic weights of 240 g and more, whereas the PHA-stimulated thymidine incorporation increased significantly (p = .015) and the proportion of EAC-binding lymphocytes increased significantly (p = .023). The PHA-stimulation of peripheral lymphocytes in patients with pathologic stage I and II disease was at the same level before and after operation, but increased significantly (less than 0.02) in the more disseminated forms. The stimulation of the lymphocytes in vitro by a cocktail of antigens, and by allogeneic cells (MLC) remained unchanged. Although the number of cases studied is rather small, it is concluded that about 10 days after, splenectomy has no demonstrable untoward effect on the cellular immunologic potency.