This case report concerns a 44-year-old woman who experienced 5 similar motor vehicle accidents, the last 3 causing severe PTSD episodes of over 6 months each, despite multiple pharmacotherapies. Following a 6th accident, severe PTSD symptoms reemerged. Forty-eight hours after this trauma, propranolol (60 mg) orally, twice a day (1.75 mg/kg/day) was begun, and the PTSD symptoms were rapidly and markedly reduced. The Clinician-Administered PTSD Rating Scale score was reduced from an initial 86 to 56 by 11 days posttrauma. To our knowledge, this is the first report of the effects of propranolol treatment on reemergent PTSD symptoms. Propranolol may be particularly efficacious in the prevention of initial or reemergent PTSD symptoms.