Serial determinations ofβ-microglobulin, lactoferrin and lysozyme in CSF were performed in 14 patients with acute cerebrovascular lesions. Marked elevations were noted in patients with cerebral bleeding or hemorrhagic infarction. Patients with infarction without signs of bleeding or with cerebrovascular lesions undetectable by computed tomography also had an increase in these proteins. The increases in CSF of β-microglobulin, lactoferrin and lysozyme could not be explained by a damaged blood-brain barrier but was believed to be a local product of the central nervous system. Peak levels of lactoferrin and lysozyme were noted on day 2–3 after onset of symptoms. Lactoferrin then declined while lysozyme remained elevated for another few days. β-microglobulin gradually increased reaching peak levels on day 4-5 and remained elevated even 2 weeks after the onset of symptoms. We suggest that the increases of lactoferrin, lysozyme and β-microglobulin reflect various inflammatory reactions mediated by granulocytes, macrophages and lymphocytes, respectively. Stroke, Vol 12, No 1, 1981