Background : To compare characteristics, treatment and out-come of patients ≥70 years with patients <70 years in a population-based non-Hodgkin's lymphoma (NHL) registry. Patients and methods : All new patients with NHL ( n = 1168) in a geographically defined region in the western part of The Netherlands were registered during a nearly 10-year period. Patient, tumour and treatment characteristics, response to therapy and survival were analysed for both age groups. An age-adjusted prognostic index was determined for elderly patients with aggressive lymphoma. Results : The elderly comprised 41% of the registered patients. There were significantly more females, a preponderance of intermediate-grade histology (diffuse large B-cell lymphoma) and a lower performance status. Incomplete staging in the elderly was mostly due to the omission of a bone marrow biopsy. With respect to WF grading the complete remission rate (except for patients with low-grade/stage I NHL, patients with extranodal NHL and for patients with intermediate grade/extensive NHL) and overall survival at five years (except for patients with low-grade/stage I NHL and for patients with intermediate-grade/extensive NHL) were significantly inferior in the elderly. With respect to the R.E.A.L. Classification the exceptions were in patients with high grade MALT lymphomas (elderly good) and patients with mantle-cell and peripheral T-cell lymphomas (younger group bad too). However, once complete remission was reached, the disease-free survival did not differ significantly between the two age groups, emphasising the importance of achieving complete remission. Although 65% of the classified elderly patients presented with intermediate-grade NHL, only 26% of the elderly patients treated with chemotherapy received anthracycline-based chemotherapy. In the elderly, lymphoma (treatment-related toxicity included) contributed to death in 70% and concomitant disease (other malignancy included) in 30%, versus 78% and 22%, respectively, for the younger group ( P = ...