Median survival of patients with leptomeningeal metastases (LM) is 4 to 6 months, with a few long-term survivors. Current prognostic factors for survival have limited value. The authors measured the CSF levels of nine inflammatory proteins in 57 patients with LM and determined their prognostic value. High interleukin (IL)-8 CSF levels predicted short-term survival independently. The data indicate that IL-8 CSF levels may serve as a prognosticator in patients with LM, but prospective validation is needed.