The neuroprotein S-100B was identified as a possible marker for primary brain damage. The objective of this prospective study was to determine the diagnostic validity of plasma measurements of S-100B in patients with minor head injury and acute alcohol intoxication. The results of S-100B plasma levels were compared to the Glasgow-Coma-Scale score, the neurological examination and the CCT data. Median S-100B levels of the CCT+ patients were significantly increased compared to those of the CCT- patients without being influenced by alcohol. Increased S-100B plasma levels seem to indicate a primary brain damage.