Between 60-80% of non-Hodgkin's lymphoma (NHL) of T-cell lineage in children, present with primary mediastinal disease. On current therapy, this and nodal low-stage disease are associated with a relatively favourable outcome. In order to evaluate whether the primary site of disease is a prognostic factor, we examined the clinical characteristics and outcome of 36 children with primary extrathoracic T-cell NHL diagnosed during a 7-year period by the United Kingdom Children's Cancer Study Group. Eight, eight, 11 and nine children had stage I, II, III and IV disease, respectively. The primary site of disease was nodal in 22, skin and subcutaneous tissue in five, abdominal in three, bone in three and at other sites in three. Eighteen (50%) had lymphoblastic, ten (28%) large cell anaplastic (LCA) and seven (19%) pleomorphic large or medium cell (PLC) tumours. In one child the histology was inconclusive. All children with lymphoblastic, three with LCA, three with PLC disease and one with unknown histology were treated on intensive, sustained and continuous leukaemia protocols. Ten, seven with LCA and three with PLC, were treated on regimens of short duration pulsed therapy and one child with PLC with radiotherapy only. The three-year event-free survival (EFS) was 78% for the group as a whole. Those with stage IV lymphoblastic disease had a significantly worse prognosis (p < 0.0005). Primary site of disease, gender, therapeutic regimen and histology were not predictive for survival. In primary extrathoracic T-cell NHL with lymphoblastic histology, leukaemia-like therapy is recommended. For non-lymphoblastic disease, in particular the Ki-1 positive tumours, evidence suggests that short duration pulsed therapy may be optimal.