A series of 147 patients, 99 in clinical stage I and 48 in stage II, with localized non-Hodgkin's lymphoma, exclusively given radiation therapy, was retrospectively analysed. Using the Kiel classification, 12 patients (8%) could not be subgrouped with certainty, 63 (43%) were designated as high-graded and 72 (49%) as low-grade malignancies according to the definitions of Gérard-Marchant et coll. (1974). Complete remission was obtained in 93 per cent of the patients in stage I and in 75 per cent in stage II. Most of the failures (68%) were high-grade malignancies. Actuarial and relapse-free survival was determined for stage I and II and stratified by microscopy and extranodal disease. All patients initially in stage I had a good prognosis irrespective of the microscopic type; 60 per cent have remained free from disease. In contrast, only 2 patients (4%, all low-grade) in stage II have remained disease-free. Thus, in stage II irradiation cannot be considered the best treatment, especially in patients with high-grade malignancy, in whom chemotherapy may be curable. In stage I, on the other hand, irradiation seems to be curative in the majority of patients irrespective of microscopic type.