This study describes the usefulness of fluid-attenuated inversion recovery (FLAIR) pulse sequence for early diagnosis and treatment of herpes encephalitis. An 8-year-old boy with suspected herpes simplex encephalitis was examined by magnetic resonance imaging at 3 days post-symptom onset. Lesions in the right thalamus and insular cortex were detected by conventional T2-weighted images and images from FLAIR pulse sequence. Bilateral temporal lesions, however, were only detected by FLAIR images.