BACKGROUND Neuron-specific enolase (NSE) and myelin basic protein (MBP) in the peripheral venous blood (PVB) have been reported to be sensitive markers for judging the prognosis of patients with head injury. However, to our knowledge, the levels of NSE and MBP in the internal jugular venous blood (IJVB) have never been studied. METHODS In 25 patients with acute head injury, blood samples were taken from the internal jugular vein and the peripheral vein at the same time before any medical or surgical procedure was performed. The levels of NSE and MBP in the both venous blood samples were measured. The time interval between injury and sampling was 1.5-8.0 hours (mean 4.3 hours). The levels of NSE and MBP in the IJVB were compared to those in the PVB. The relationship between the clinical outcome and the serum levels of those was evaluated. RESULTS The levels of NSE and MBP in the IJVB were almost equal to those in the PVB. The levels of NSE and MBP were significantly higher in the patients who died than in those who survived. In the survivors, the levels of NSE and MBP in the IJVB were 17.6 +/- 11.4 ng/ml and 1.4 +/- 1.5 ng/ml, whereas in the patients who died, both levels were elevated to 51.3 +/- 27.3 ng/ml (p < 0.005) and to 11.3 +/- 9.5 ng/ml (p < 0.01), respectively. CONCLUSIONS The assay of serum NSE and MBP levels provides a reliable laboratory indicator of the degree of brain damage and allows early prediction of the prognosis in patients with acute head injury.