We report a patient with general paresis, whose magnetic resonance image (MRI) showed a T2 high-intensity lesion in bilateral mesial temporal regions. Serum rapid plasma reagin test showed reactive at 64 dilutions and serum Treponema pallidum haemagglutination test was 1:20480. Cerebrospinal fluid analysis showed: RBC 111/mm3, WBC 8/mm3, Venereal Disease Research Laboratory reactive at 1 dilution and protein 60 mg/dl. His neuropsychiatric symptoms recovered gradually after penicillin treatment two months later. Repeated MRI revealed resolution of the bilateral mesial temporal lesions. We demonstrated the first Taiwanese patient with general paresis whose clinical improvement was associated with the disappearance of the temporal lobe MRI abnormality. The diagnosis of neurosyphilis must be considered when MRI shows mesial temporal lesions. MRI may be used to predict prognosis in patients with general paresis.