Silymarin, that is extracted from milk thistle (Silybum marianum), was used as drug of hepatoprotection from 2000 years ago and known to have an antioxidative and an anti-inflammatory effects.We examine the effect of the silymarin on delayed neuronal cell death of the hippocampus in rats. We induced transient cerebral ischemia, occluding the bilateral carotid arteries for 20 minutes and sacrificed the rat in a week after the surgery. Silymarin was administered 200 mg/kg body weight orally. The rats were divided into four groups, sham operated group (sham), group which was underwent the surgery (control), group which was treated by silymarin before 1 week and after 1 week the surgery (pre), group which was treated by silymarin after 1 week the surgery (post). We didn't detect the delayed neuronal cell death in sham group. In FJB staining, the amount of delayed neuronal cell death in pre and post groups were decreased significantly in comparison to that in the control group. There was no difference between the pre and post groups. In contrast to the large amount of cell death by autophagy in the control group, only a small number of cell death by autophagy was observed in both pre and post groups. We found that silymarin has a protective effect on delayed neuronal cell death in the hippocampus.