We retrospectively analyzed 114 patients with non-Hodgkin's lymphoma, clinical stages I and II, classified by the criteria of Rappaport and treated by radiotherapy alone. Of 84 patients classifiable, one-third were nodular and two-thirds diffuse lymphomas. Berkson-Gage actuarial and relapse-free survivals were determined for these two groups and for subgroups stratified by histology, stage, and by presence or absence of extranodal disease. Five year relapse-free and overall survivals were 83% and 100%, respectively, for the nodular group and 37% and 59% for the diffuse group. Extranodal involvement was less frequent in the nodular (19%) than in the diffuse (52%) group, where it was associated with Stage IE disease and increased relapse-free and actuarial survival. Histopathological subtype in the diffuse group (histiocytic versus combined lymphocytic poorly differentiated and mixed lymphocytic-histiocytic) did not influence survival. Extranodal involvement and stage I disease were associated with better survival in the diffuse histiocytic group. Successful radiotherapy for all stages of disease, all histologies, was not correlated with extended versus involved fields, and 89% of the relapses in the entire series were by wide dissemination.