Peripheral blood mononuclear cells from 20 previously untreated adult patients with Hodgkin's disease were evaluated for the ability to induce suppressor cell activity following in vitro exposure to concanavalin A (Con A). Suppression of proliferative responses by autologous as well as normal allogeneic peripheral blood lymphocytes to the mitogen phytohemagglutinin (PHA) was assessed using suppressor/responder cell ratios of 2:1 and 1:1. The generation of Con A-induced suppressor cell activity (T-T suppression) was deficient in 35% of the patients (7/20) by the criteria employed. Peripheral blood leukocytes from 18% of patients (2/11) with localized disease (stages I and II), and 56% of patients (5/9) with widespread disease (stages III and IV) exhibited subnormal suppressor activity. There was no correlation between absolute lymphocyte count, absolute T-cell number, or proliferative response to PHA, and Con A-induced suppressor cell activity. This impaired ability to generate Con A-induced suppressor cells in Hodgkin's disease may reflect a functional T-cell deficit, or the suppressive influence of abnormal circulating monocytes.