We studied the diagnostic value of detecting protein 14-3-3 and of assaying neuronal specific enolase (NSE) in the cerebrospinal fluid of 150 patients with suspected sporadic Creutzfeldt-Jakob disease registered in an epidemiology research program between 1991 and 1996. Sensitivity and specificity of these two tests were high. This study confirms results reported earlier and authorizes a new definition of Creutzfeldt-Jakob disease which gives protein 14-3-3 the same diagnostic value as EEG recordings for classifying sporadic cases.