Patients with untreated active Hodgkin's disease (HD) have a defect in cell-mediated immunity. After therapy many HD patients still have long lasting abnormalities in T cell number and function. We examined whether NK activity is also permanently impaired in HD patients in remission. The mean NK activity of peripheral blood lymphocytes from 42 patients who were disease-free for 6-150 months was not different from that of healthy controls. Augmentation of NK activity after treatment of the cells by interferon in vitro was equal for patients and controls. Normal NK activity in HD in remission was independent of disease stage, age, remission duration and mode of therapy. Measuring PHA-induced lymphocyte proliferation and NK activity simultaneously demonstrates that patients with impaired cell-mediated immunity do not have concomitant reduction of NK activity. We conclude that NK activity in HD in remission is independent of decreased T cell mediated immunity. In addition, NK is resistant to long term suppression by the chemotherapy and radiation protocols that are used in HD.