Cardiopulmonary monitoring may be desirable during magnetic resonance imaging (MRI) of hemodynamically unstable patients, but must be performed with great caution. This case report describes a severe burn associated with pulse oximetry use during MRI scanning. Risk of this injury is greatest in infants and in individuals with obtundation, general anesthesia, insensate limbs or impairments of verbal communication. Several safety precautions are described. Preparation and monitoring of patients undergoing MRI scanning with cardiopulmonary monitoring should be performed only by specially trained personnel.