Williams syndrome is a complex syndrome characterized by developmental abnormalities, craniofacial dysmorphic features, and cardiac anomalies. Sudden death has been described as a very common complication associated with anesthesia, surgery, and procedures in this population. Anatomical abnormalities associated with the heart pre-dispose these individuals to sudden death. In addition to a sudden and rapid downhill course, lack of response to resuscitation is another significant feature seen in these patients. The authors report a five-year-old male with Williams syndrome, hypothyroidism, and attention deficit hyperactivity disorder. He suffered an anaphylactic reaction during CT imaging with contrast. Resuscitation was unsuccessful. Previous reports regarding the anesthetic management of patients with Williams are reviewed and the potential for sudden death or peri-procedure related cardiac arrest discussed in this report. The authors also review reasons for refractoriness to defined resuscitation guidelines in this patient population.