BACKGROUND To describe a case series of nasal natural killer (NK)/T-cell lymphoma (NKTL) with orbital and central nervous system extension. METHODS This is a retrospective study. The medical records of 9 patients with a diagnosis of NKTL were reviewed. All patients had a positive biopsy for CD3, CD56, T-cell-restricted intracellular antigen-1, and granzyme expression and CT imaging of nose, sinuses, orbits, and brain. Five patients were also examined with MRI. RESULTS Orbital extension occurred in 6 patients. All had extraocular muscle enlargement and 5 showed signs of perineural spread. CONCLUSIONS NKTL is a polymorphous disease. Extraocular muscle involvement and perineural spread are overlooked features that explain dissemination of the tumor to both the orbit and the central nervous system.