We report unusual radiographic findings which were seen during the management of a patient with anaplastic astrocytoma. An enhanced region in a gyrus of the right frontal lobe was demonstrated in a 38-year-old woman who had had a generalized seizure. Following treatment with steroid- and osmotherapy, this enhanced region decreased clearly on magnetic resonance imaging (MRI). Six months later, an enhancing mass lesion appeared in the same position. After surgery, this was diagnosed as being an anaplastic astrocytoma. It is speculated that the initial enhancement was caused by transient dysfunction of the blood-brain following the seizure. In this case, the most important radiologic image was a T2-weighted image of MRI which was able to demonstrate the existence of the lesion until the time of its removal by surgery.