A retrospective analysis was performed of 451 adult patients with clinical stage 1/1E non-Hodgkin's lymphoma treated initially with radiotherapy alone. Histopathologically 208 patients had low-grade disease and 243 patients high-grade disease. The complete remission (CR) rate was higher in patients with low-grade disease (98%) than in those with high-grade disease (84%) (P < 0.0001). The relapse rate was similar in both histological categories, and relapse usually occurred within 5 years. The resulting overall actuarial percentage of patients achieving CR and remaining disease free (at 10 years) was 47% in patients with low-grade disease and 45% for those with high-grade disease. Salvage therapy was frequently successful in younger patients, and the overall cause-specific survival at 10 years was 71% for low-grade disease and 67% for high-grade disease. In those patients under 60 years of age at diagnosis, the overall cause-specific survival at 10 years was 84% and 80% for those with low-grade and high-grade disease respectively. These long-term results in young patients with clinical stage 1 disease are encouraging, and it will be difficult to demonstrate improved survival with initial chemotherapy either with or without radiotherapy, until new prognostic factors are found to identify poor-risk patients.