The aim of this study was to determine the relationship between serum and cerebrospinal fluid (CSF) magnesium(Mg+2) levels, Glasgow Coma Scores (GCS), and 7-day mortality in acute stroke patients. Patients with acute ischemic or hemorrhagic stroke arriving within the first 3 h of symptoms were included in the study. The control group consisted of healthy volunteers. GCS was determined, and blood and CSF samples were taken in order to establish serum and CSF glucose, Mg+2, sodium, potassium, calcium, and chlorine levels.Mortality was recorded at 7 days after admission. CSF Mg+2 in the ischemic infarct group was significantly lower than in the control group (p=0.006). CSF Mg+2 in the ischemic infarct patients with a GCS < or = 8 were significantly lower (p=0.002) than controls and in ischemic infarct patients with a GCS > or = 9. In the ischemic stroke patients, CSF Mg+2 and GCS were significantly correlated (r=55, p=0.031). CSF Mg+2 levels in ischemic stroke patients who died within 7 days were significantly lower than controls, ischemic stroke patients who survived, and hemorrhagic stroke patients who died (p=0.002, p=0.042, and p=0.005,respectively). Low CSF Mg+2 levels in patients with acute ischemic stoke at admission predicted a higher 1-week mortality.