In this study of 127 previously untreated adult patients with Hodgkin's disease and 167 age- and sex-matched controls, highly purified blood lymphocytes were studied for E+ receptors; their spontaneous DNA synthesis and that induced by concanavalin A, pokeweed mitogen, or purified protein derivative of tuberculin were measured as incorporation of 14C-thymidine. T-cell counts and the response to mitogens and antigen were significantly decreased in the patients, while the spontaneous lymphocyte activity was increased. Forty-nine patients had died after a mean observation time of 6 years. In these patients, there had been an increase in spontaneous DNA synthesis and a decrease in that induced by mitogens and antigen. These differences also remained significant when patients who died were compared with surviving patients in stages I-II. The 5-year survival rate of "bad immunology" patients was 30% as compared to 80% for the remainder. We suggest that these lymphocyte tests should be considered in an "immunologic staging system," which may give guidance in the future management of patients with Hodgkin's disease.