The effect of the dopaminergic antagonist haloperidol on the permeability of the blood-brain barrier (BBB) to [14C]alpha-aminoisobutyric acid was studied in 10-12- and 28-30-week old rats. Following the intraperitoneal injection of haloperidol (1 mg kg-1), an increase in the permeability of the BBB, with respect to younger animals, was observed within the occipital cortex, striatum, hippocampus and hypothalamus in the older rats. No correlation was found between haloperidol-induced changes and age-related differences in the permeability of the BBB. Such age-associated increase in the vulnerability of the BBB when challenged with haloperidol might be related to a deterioration of the dopaminergic control of cerebrovascular permeability.