Significant elevation of glutamic acid and glutamine concentrations in CSF was observed in hepatic encephalopathic patients with fulminant hepatitis and liver cirrhosis. However, the ratios of CSF glutamic acid to CSF glutamine levels and of CSF to serum glutamic acid and glutamine levels were significantly higher only in cirrhotic patients with hepatic encephalopathy. CSF glutamine levels were positively correlated with blood ammonia and CSF tyrosine levels in cirrhotic patients. The results indicate that CSF glutamic acid and glutamine levels are important tools in diagnosing hepatic encephalopathy in severe liver disease.