Ventricular concentrations of homovanillic acid (HVA) and 5-hydroxyindole-acetic acid (5HIAA) were measured in 7 patients a few days after a severe traumatic brain injury. Both acid metabolites were elevated in respect to control patients values, however, the rise was more consistent for 5HIAA (258 +/- 86 ng/ml) with a 5HIAA/HVA ratio of 0.85 +/- 0.35. The data support previous hypothesis on the profound involvement of serotoninergic structures in the early stages of acute traumatic brain syndromes and on the role of 5HT in maintaining edema and vasospasm.