Abstract
Cerebrospinal fluid (CSF) samples were tested for their cytotoxicity to polymorphonuclear neutrophil leucocytes (PMN) using a 51Cr release assay. Most samples from patients with pyogenic meningitis damaged PMN while normal CSF samples did not. No difference was found between the cytotoxic activity of CSF from patients with pneumococcal meningitis and from patients with meningococcal meningitis. It is, therefore, unlikely that a CSF leucocidin plays an important part in producing the high mortality of pneumococcal meningitis.