We studied CSF CK and LDH isoenzyme activities in 27 patients with severe head injury and in 10 patients with chronic hydrocephalus not related to trauma. CSF enzymes showed an increased activity immediately after trauma, contrasting with the low values measured in the patients with hydrocephalus. In severe head injury, we found a correlation between enzyme release and brain dysfunction assessed according to two methods: the Glasgow coma scale (GCS), and the Liege coma scale (LCS) which uses elements of the GCS and the study of 5 brain stem reflexes. The correlation between enzyme activity and the Liege coma scores is better than that observed with the Glasgow coma scores. High enzyme activity is associated with a bad outcome at six months. It has a prognostic value on so far as it reflects the severity of traumatic structural brain damage