Following complete remission of non-Hodgkin's lymphoma by chemotherapy, irradiation or both, 44 patients were studied to assess the value of bacille Calmette-Guérin (BCG) as maintenance therapy. Patients with stage LI, EI or EII disease were allocated at random to receive BCG or no further maintenance therapy, and those with stage LII, LIII, EIII or IV disease received BCG therapy or orally administered cyclophosphamide. BCG had no effect on the duration of remission or the overall survival from the time of randomization. However, after the first recurrence there was a significant improvement in survival in the patients who had received BCG maintenance therapy.