Within a seven year period, 1597 newly diagnosed cases of non-Hodgkins lymphoma (NHL) were included in a Danish population-based NHL-register. Of these, 602 (38%) were aged 70 or older (age range 70-94, median: 76.8) and represented the population defined as "elderly" patients in the present study. Their average annual incidence rate was 35.7/10(5), as compared to 6.6/10(5) for patients aged < 70 (overall annual incidence: 9.5/105). Localised cases (stage I and II) and extranodal manifestations were more frequent among elderly patients. The most common sites of extranodal involvement were stomach (21% of all extranodal cases) and bone marrow (16%). Histologically, follicular centroblastic/centrocytic cases were found to be less frequent (p < 0.01) in elderly patients as compared to their younger counterparts (< 70 years), who on the other hand had a lower occurrence of diffuse centroblastic cases (p < 0.01). Overall seven year survival for the elderly patient population was 35% (median: 1.7 years), and for patients aged < 70 it was 57%. This difference persisted after correction for apparently NHL-unrelated deaths (52% vs. 66% respectively, p < 0.0001). The following poor prognostic factors for elderly patients were identified by multivariate analysis: hepatic involvement, presence of B-symptoms, high-grade histology and elevated s-LDH. The corresponding relative risk values were respectively 2.4, 2.2, 1.9 and 1.6.