Patients with suspected Creutzfeldt-Jakob disease (CJD) often have routine cerebrospinal fluid (CSF) analysis performed to exclude treatable inflammatory conditions; however, little information is available about the range of results obtained for CSF tests in patients with sporadic CJD and other transmissible spongiform encephalopathies (TSE). Data from 450 patients with sporadic CJD and 47 patients with other TSEs were collected as part of an EC-supported multinational study. Raised white cell counts of >5 cells/microl were found in three of 298 patients with sporadic CJD, with two cell counts of 7 cells/microl and one of 20 cells/microl. Total protein concentrations of >0.9 g/l were found in five of 438 patients with sporadic CJD, although none had a concentration of >1 g/l. CSF oligoclonal IgG was detected in eight of 182 sporadic CJD patients. Of the patients with other TSEs, six had elevated cell counts ranging from 6 to 14 cells/microl but none had total protein concentrations of >0.9 g/l and one patient had detectable oligoclonal IgG. None of the patients with sporadic CJD or other TSEs had abnormalities in all three tests.