The incidence of malignant lymphomas in the nasal cavity and paranasal sinuses was found to be 0.17% of all malignant lymphomas and 0.44% of all extranodal malignant lymphomas registered in the Kiel Lymph Node Registry from 1972 to 1987. Fifty-nine cases of malignant lymphoma presenting in the nasal cavity and paranasal sinuses were investigated with morphological and immunological methods. The median age of the patients was 64.5 years, with a female predominance (m:f = 0.87:1). In the 59 cases a marked preponderance of B-cell lymphomas was found (centroblastic n = 15, immunoblastic n = 8, Burkitt's lymphoma n = 6, Immunocytoma n = 3, centrocytic n = 1, centroblastic/centrocytic n = 1, plasmacytic n = 11); only a small number (n = 5) was of T-cell lineage (pleomorphic types). Nine further cases could not be assigned with certainty to either the T or B cell system. Angiocentricity with infiltration and destruction of vessel walls by tumour cells was demonstrated only in the T-cell lymphomas; the B-cell lymphomas, in contrast, often surrounded and compressed blood vessels with intact endothelium. No similarity to malignant lymphomas of mucosa associated lymphoid tissue, such as those in the gastrointestinal tract, was detected.