A 69-year-old woman developed seizures after cerebral angiography immediately preceded by coronary angiography. The preceding coronary angiography resulted in hyperconcentration, hyperosmolar loading, and overdosing of the nonionic contrast medium. A CT examination demonstrated gyriform enhancement throughout the left cortex and the left basal ganglia. Preloading with contrast material, as in this case, predisposes to disruption of the blood-brain barrier during selective common carotid or vertebral artery injection with nonionic contrast.