The authors describe a 58-year-old man with fatigue, anorexia, weight loss, and pain in the lumbar region and lower abdomen. Nine years earlier, he had a myocardial infarction, and had recently recovered from a transient ischemic attack. Physical examination showed xanthelasma and bruits over both iliac arteries, with weak distal pulses. Biochemical examination revealed an inflammatory condition (erythrocyte sedimentation rate, 70 mm over I hour). Findings of a chest radiograph and abdominal ultrasound were normal. F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) showed intense FDG uptake surrounding the aorta Magnetic resonance (MR) angiography revealed extensive atheromatosis of the abdominal aorta and the iliac arteries. The aorta was surrounded by an inhomogeneous mass, and periaortitis was diagnosed. After treatment with methylprednisolone (64 mg/day), the patient recovered rapidly.