A 40-year-old man was admitted to our hospital for surgical treatment of aortic insufficiency and coronary ostial stenosis. Histopathology and serological tests revealed a syphilitic aortitis. 18F-FDG PET/CTwas performed to assess the extent of aortitis, showing increased radiopharmaceutical uptake along the ascending aortic wall. A repeated FDG PET/CTafter antibiotic therapy showed a markedly reduced uptake in the aortic wall, suggesting resolution of the infection according to clinical and serological data. This case highlights the usefulness of FDG PET/CT for the assessment of disease extent and treatment response in patients with syphilitic aortitis.