We retrospectively analyzed the MR findings of 12 patients with herpes simplex encephalitis (HSE) (8 months-64 years old). MR imaging was performed on either a 0.5T (6 patients) or 2.0T (6 patients) superconducting unit with spin echo pulse sequences. The most common and characterristic MR finding consisted of non-hemorrhgic lesions in the cortices of the temporal lobes (12), and insula(6), either bilateral (7) or unilateral (5). The frontal lobe and cingulate gyrus were involved in 4 and 2 patients respectively. Petechial hemorrhge was found in 3 patients. Non-hemorrhagic lesions were shown as high signal intensities on proton and T2WI, and iso-or low signal intensities on T1WI. In conclusion, MR imaging findings described above appear to be characteristic of HSE and were found to be extremely valuable in the diagnosis of HSE.