Granulocyte colony-stimulating factor(G-CSF)is known to cause bone pain, headache, and fatigue as side effects. We experienced 2 cases of aortitis caused by pegfilgrastim(PEG-G)administration. Case 1: A 50s woman with breast cancer started FEC therapy with PEG-G as neoadjuvant chemotherapy. She developed a fever in the 38℃ range, and chest CT showed wall thickening in the aortic arch. She was diagnosed with aortitis and administration of prednisolone was started, and the fever resolved and the general condition improved dramatically. Case 2: A 70s woman was started TC therapy with PEG-G as adjuvant chemotherapy after surgery. Fever, anorexia, and epigastralgia appeared. A CT scan of the abdomen revealed thickening of the abdominal aortic wall from the thoracoabdominal transition area to the renal artery bifurcation. She was diagnosed with PEG-G-induced aortitis, and administration of prednisolone was started. The fever resolved and the pain disappeared. Although the symptoms of G-CSF-induced aortitis are nonspecific, it is relatively easy to diagnose by CT and should be considered when a fever develops after G-CSF administration.