The results of treatment in 175 consecutive patients with nonHodgkin lymphoma (NHL) clinical stage I treated between 1969 and 1984 were analysed according to different pretreatment prognostic variables. Treatment consisted of radiotherapy in 166 of the 175 patients. The estimated 5 and 10-year disease-free survival rates (DFS) were 63% and 60% and the survival rates at 5 and 10 years 82% and 76% respectively. Lymphomas arising from gut-associated lymphoid tissue, i.e. Waldeyer's ring, the thyroid and the gastrointestinal tract had a more favourable clinical course (10-year projected DFS 83%) than nodal (50%) and other extranodal lymphomas. Although the number of patients with other extranodal sites was small, sites such as testis, nasal cavity, paranasal sinus and extradural space seemed to have a high relapse rate. Unfavourable clinical courses were also observed among nodal high-grade NHL if the lymph nodes were larger than 5 cm in diameter. Chemotherapy before radiotherapy may be recommended in NHL subgroups with a high relapse rate and which today are potentially curable with chemotherapy, i.e. highgrade NHL. This study indicates that large nodal lymphomas and some extranodal sites belong to this group.