We describe a 42-yr-old woman scheduled for emergency cesarean section who had sudden cardiopulmonary arrest just before induction of general anesthesia. Hypermagnesemia, caused by accidental overdose of magnesium sulfate during transportation to the operating room, was the primary cause of this life-threatening event. Anesthetic management after such events and a brief summary of the literature regarding iatrogenic hypermagnesemia in obsteric patients are provided.