Vaccination against pandemic novel infl uenza A (H1N1) in Taiwan started after the World Health Organization raised the pandemic alert level to phase 6 on June 11, 2009. Previous reports of rare neurological complications of H1N1 infl uenza vaccination, such as Guillain-Barré syndrome and acute disseminated encephalomyelitis, raised concerns about vaccine safety. We report a rare case of a previously healthy young man who developed postural tachycardia syndrome (POTS) with cerebral hypoperfusion (as detected by a head-up tilt test and brain single photon emission computed tomography) following vaccination against novel H1N1 infl uenza. Orthostatic symptoms, including lightheadedness, palpitation, and near syncope, obviously impaired the patient’s daily activity. Early awareness of the possible association between new onset POTS and influenza vaccination may facilitate evaluation and determination of appropriate treatment.