The changes in the permeability of the blood-brain barrier (BBB) during bicuculline-induced seizures were investigated in ovariectomized female and orchidectomized male rats. The rats were anesthetized with diethyl ether. Evans blue, which was used as a BBB tracer, was injected into femoral vein 5 min before administering bicuculline to induce grandmal seizures. Ten groups of rats were studied: Group I: control female; Group II: control male; Group III: intact female + bicuculline; Group IV: intact male + bicuculline; Group V: ovariectomized female; Group VI: orchidectomized male; Group VII: ovariectomized female + bicuculline; Group VIII: orchidectomized male + bicuculline (1.2 mg/kg, i.v.); Group IX: ovariectomized female + estrogen + bicuculline; Group X: orchidectomized male + estrogen + bicuculline. Adult male and female rats were orchidectomized and ovariectomized 3 weeks before the experiments, or sham operated under general anesthesia. During bicucculline-induced seizures, the mean arterial blood pressure increased significantly in both intact and ovariectomized and orchidectomized rats. BBB lesions were present in 80 percent of intact female rats and 50 percent of ovariectomized rats after bicuculline-induced seizures. This difference between intact and ovariectomized rats was found to be significant (p < 0.01). There was no statistically significant change in the BBB permeability between intact and orchidectomized rats after convulsion. Generating seizures in both ovariectomized and orchidectomised rats, after administrating of estrogen, did not lead to any significant alteration in BBB permeability. Our results suggest that the extravasation of Evans blue albumin was most pronounced in the brain of intact female rats when compared to ovariectomized rats after bicuculline-induced seizures. After administrating estrogen, the decreased BBB permeability values of ovariectomised rats could not reach the values in intact rats.