The records of 148 consecutive patients with Ann Arbor stage I and II large-cell lymphoma treated with primary radiation therapy with or without adjuvant chemotherapy were analyzed retrospectively for pretreatment prognostic variables and results of treatment. For patients treated with radiation to fields on one side of the diaphragm, the 5 year freedom-from-relapse rate was 25% and the survival rate was 35%, but for those given additional transdiaphragmatic radiation or for those given radiation plus adjuvant chemotherapy, the rates were both approximately 67%. In a multivariate analysis, the only significant pretreatment prognostic variables were the number of sites of involvement and bulk of disease, with relapse as the endpoint. For patients treated with radiation to both sides of the diaphragm or with radiation plus adjuvant chemotherapy, the 5-year freedom-from-relapse rate was 82% for the group with a favorable prognosis (with less than three sites of involvement and a mass size of less than 10 cm) and 55% for those with an unfavorable prognosis.