To test the correlation between cerebrospinal fluid (CSF) glutamine level and hepatic encephalopathy, measurements were made in 86 patients. In 51 without liver disease, mean CSF glutamine level was 12.6 ± 5.1 mg/100 ml. In nine patients with liver disease but without clinical encephalopathy, the mean value was 21.6 ± 6.2 mg/100 ml and in 26 patients with varying degrees of precoma and coma it was 40.3 ± 14 mg/100 ml. There was a fair correlation between the severity of encephalopathy and the glutamine level. The CSF glutamine test, an easily performed biochemical evaluation, seems useful in the diagnosis of hepatic encephalopathy and in the assessment of its severity.