Primary lymphoma of the central nervous system (PL-CNS) is a tumor the incidence of which has increased in the last ten years and is frequently associated to immunesuppressed states. It is a non-Hodgkin lymphoma, usually diffuse and of type B. The clinical presentation form is non-specific and for its diagnosis CT scan data are usefull although it is necesary to confirm this diagnosis with a biopsy. Treatment consists on holocraneal radiotherapy associated to chemotherapy. Prognosis is obscure since local relapses are very frequent although its extension to other sites outside the CNS is rare.