This study was designed to evaluate the role of elevated blood pressure on cerebrovascular permeability and brain tissue specific gravity during epileptic seizures induced by Pentylenetetrazole (PTZ). The experiments were carried out on Wistar rats. Specific gravity was measured bilaterally in 10 regional brain areas and Evans-blue passage (across blood-brain barrier) was spectrophotometrically measured in 6 brain areas. Animals were divided into four groups: they received i.v. either saline, 80mg/kg PTZ (convulsive dose), 40mg/kg PTZ (subconvulsive dose) or 80mg/kg PTZ+phentolamine. 80 mg/kg PTZ induced significantly an increase in blood pressure, in specific gravity and in Evans-blue passage. 40mg/kg PTZ induced an increase in blood pressure and caused small changes in specific gravity but not in Evans-blue passage. The last group, in which the rise in blood pressure was prevented with Phentolamine, also showed a significant increase in brain specific gravity and in Evans-blue passage. The results clearly show that the increased blood pressure may contribute to but is not entirely responsible for the changes in the cerebrovascular permeability induced by epileptic seizures.