In a Danish population-based non-Hodgkin lymphoma (NHL) registry, 1257 newly diagnosed NHL cases were registered over a 5-year period. Of these, 463 (37%) were extranodal. The gastrointestinal tract was the most common site of extranodal involvement (30% of the cases). Histologically, 44% of all extranodal NHL cases had high-grade, 17% intermediate and 27% low-grade features, while 12% were unclassified. The most common histological subtype (Kiel) was the centroblastic diffuse (23% of cases). 50% of all extranodal NHL were localised (stage IE or IIE) and 27% had B symptoms. Site-specific features included a strong age-correlation for thyroid and testes lymphoma (greater than 50 years) and a high prevalence of female cases in thyroid and salivary glands lymphomas (M/F 0.14 and 0.30, respectively). Overall 7-year survival for extranodal NHL was 46% (median 4.9 years). Poor prognosis patients could be identified by the presence of one or more of the following presentation characteristics: age greater than 65 years, B symptoms, high-grade histology, disseminated disease, elevated s-IgA and hyperuricaemia. Relative risk values ranged from 2.1 for age and B symptoms to 1.7 for hyperuricaemia.