Nasal natural killer (NK)/T cell lymphoma is an aggressive subtype of non-Hodgkin lymphomas, usually with a broad morphological spectrum, necrosis and angioinvasion, and is closely associated with Epstein-Barr virus (EBV) infection. We herein report a unique case of nasal NK/T cell lymphoma with frequent complete remission and relapse 12 years of follow up. A 9-year-old girl was diagnosed as having nasal NK/T cell lymphoma in 1995. The histological features were typical with diffuse lymphoid cell infiltration and angiocentric destruction. At the time of third relapse, however, biopsy showed infiltration of small sized lymphoid cells without necrosis and ulceration. These lymphoid cells were positive for both NK/T cell phenotype and EBV-encoded small RNAs. The tumor regressed spontaneously after biopsy and her clinical symptoms subsided. When she was admitted to the hospital in 2006 she had an extensive destructive lesion in the nasal cavity. These findings represent a rare case, in which histological findings changed in each time of relapse. [J Clin Exp Hematopathol 50(1) : 65-69, 2010]