This study was designed to investigate whether myelin basic protein (MBP) in cerebrospinal fluid (CSF) can be a predictive marker of delayed encephalopathy from carbon monoxide (CO) poisoning. Five patients with CO poisoning were included in the study. The CSF was serially sampled to determine the MBP concentration. All patients were classified into group DE or group non-DE according to whether delayed encephalopathy developed or not. In all 3 patients in group DE, the MBP levels in the CSF were markedly elevated preceding the clinical manifestations of delayed encephalopathy. In both group non-DE patients, the MBP concentrations in the CSF were never elevated. Elevated MBP concentrations in the CSF may represent a predictive marker of delayed encephalopathy from CO poisoning, leading to a more appropriate triage of patients with CO poisoning.