The authors studied the immunophenotype of nine sinonasal lymphomas using a panel of monoclonal antibodies that react with fixed, paraffin-embedded material (EMA, CAM 5.2, CD45, CD37 IMB-1), MB-2, L-26, CDw75 [LN-1], CD45RA [4 KB-5], CD43 [MT-1], and CD45ROIUCHL-1)). There were seven men and two women, with a mean age of 64 years (range, 9-89 years) and median age of 56 years. Three tumors were limited to the nasal cavity, and the other six had multiple sites of involvement, including the nasal cavity (five), antrum (six), ethmoid (two), orbit (two), and hard palate (one). Histologically, one was a lymphoblastic lymphoma (LBL), one was small cleaved-cell lymphoma (SCCL), three were mixed-cell lymphomas (MCLs), and four were large cell lymphomas (LCLs). Four cases were T-cell lymphomas (one SCCL, three MCLs), four were B-cell neoplasms (four LCLs), and one was of uncertain lineage (LBL).Angioinvasion, coagulative necrosis, and epitheliotropism were seen in the T-cell lymphomas. Extranasal dissemination was seen in four cases: one LBL that involved the lymph nodes, skin, and testes 15 months after diagnosis; one B-LCL that involved the skin 9 months after diagnosis; and one B-LCL and one TMCL that involved the gastric mucosa and lung simultaneously with nasal presentation. This study shows a higher predominance of B-cell lymphomas in the sinonasal region than previously reported in Oriental populations. However, the T:B ratio of these lymphomas is still greater than that observed for primary lymph node-based neoplasms.