Somnolence syndrome classically occurs in children after cranial irradiation for acute lymphocytic leukemia. Symptoms include somnolence, fever, nausea and vomiting, and headache. The authors report a 29 year-old female who developed symptoms compatible with the somnolence syndrome after completing radiation therapy for a benign meningioma near the pineal region. Five weeks after completing conformal radiation therapy (54 Gy), she developed profound fatigue, headaches, and 102-degree fevers. Physical examination and routine laboratory work were unrevealing. Imaging was not performed. Prednisone was prescribed and within 1 week her symptoms had largely resolved. This is the first report of the somnolence syndrome after focal radiation therapy. The possible etiology of the somnolence syndrome is discussed.