Plasma proteins were used as an endogenous marker of blood-brain barrier damage in 19 patients dying with traumatic cortical contusions. Patients survived for a few hours to 31 days after head injury. Eight proteins (M WT 61-2,500 x 10(3) were demonstrated with standard immunohistochemical techniques. Proteins were not found in "control" brains or in macroscopically normal parasagittal cortex in the head injury patients. Proteins were found in all of the macroscopic contusion in all brains. Protein leakage appeared to be from the contusion itself. Protein staining around histologically normal vessels was unusual. There was a gradient of staining from the macroscopic contusion into the surrounding brain. There was a trend for staining to be most marked between 3 and 8 days survival after head injury. There was no gradient of leakage by molecular size of the protein.