Meningeal metastasis occurs in 3-8% of all cancer patients, producing neurologic morbidity and a high mortality. Diagnosis is best established by the demonstration of malignant cells in the cerebrospinal fluid. However, in patients with known cancer, MR scan with gadolinium may be diagnostic when subarachnoid nodules can be demonstrated in the head or spine. Therapy usually involves radiotherapy to symptomatic sites, often followed by intrathecal chemotherapy. Intrathecal chemotherapy is best delivered by an intraventricular reservoir system but can also be delivered by repeated lumbar puncture. Methotrexate, cytarabine and thiotepa are the most common agents instilled into the subarachnoid space. Their limited efficacy can be explained by their restricted spectrum of antitumor activity. Patients with leptomeningeal metastasis from leukemia, lymphoma or breast cancer tend to respond best and this may, in part, be attributed to the relative sensitivity of these primary tumor types to the agents administered intrathecally. Systemic chemotherapy may prove a more attractive alternative to intrathecal drugs since it can penetrate into bulky disease, reach all areas of the subarachnoid space, and not be restricted by CSF bulk flow. The prognosis for patients with leptomeningeal metastasis is poor, most individuals surviving a median of only about four months. Occasional patients do have prolonged survival and improvement of their neurologic function.