The peripheral nerves are a very rare site of origin for primary lymphoma. A 52-year-old man presented with progressive paresthesias and numbness of the right lower extremity, associated with radiating pain from the posterior thigh to the foot. Electromyogram indicated nerve origin impairment the right lower extremity. Emission computed tomography; chest computed tomography; abdominal ultrasound and bone marrow biopsy were performed to exclude a systemic lymphoma. Magnetic resonance imaging studies revealed a solitary fusiform mass along the right sciatic nerve, at last pathological examination confirmed the primary large B-cell non-Hodgkin's lymphoma of the sciatic nerve. © 2009 Elsevier Ireland Ltd. All rights reserved.