The pediatric sedative combination of meperidine, promethazine, and chlorpromazine (MPC) has been widely used for more than 40 years. Despite its relatively poor efficacy and questionable safety profile, many emergency departments (EDs) continue to stock specially formulated mixtures of these three agents. We report a case of iatrogenic cardiac arrest in a 2-month-old infant in whom a consulting resident administered too much MPC (10 times the expected dose) by the wrong route (intravenous instead of intramuscular). The child was successfully resuscitated with no apparent neurologic deficit. Subsequently, we have removed MPC entirely from our ED and instituted a policy restricting ED procedural sedation privileges to emergency physicians. We urge other EDs to do likewise.