Rituximab is the first monoclonal antibody to receive FDA approval in the treatment of cancer. Intravenous administration of rituximab has been demonstrated to lead to prolongation of survival when used in combination with chemotherapy in the treatment of patients with systemic non-Hodgkin's lymphoma. We have previously demonstrated that a small fraction of Rituximab administered intravenously is able to cross the blood-brain-barrier into the brain and we have also previously demonstrated that direct intraventricular administration of Rituximab is able to achieve high concentrations within the cerebrospinal fluid ventricles and lumbar sac.