Epinephrine overdose induces many negative complications in adults because of its alpha- and beta-adrenoreceptor activity. However, complications in newborns or children are rarely described. A 4-day-old, 2004-g female newborn was inadvertently given epinephrine at 100 times the usual dose; she developed hypokalemia and rhabdomyolysis. A nurse erroneously administered 2 mg of epinephrine 1:1000 (1 mg/ml) into a peripheral intravenous line in the patient's right leg. Her potassium level decreased to 2.2 mEq/L. An infusion of potassium chloride 2 mEq/kg/day over 80 hours was required to correct the hypokalemia. Rhabdomyolysis was diagnosed and confirmed from laboratory results of an elevated creatine kinase level (peak 4124 U/L), with 100% creatine kinase-MM isoenzymes. No obvious long-term sequelae were observed. Effective ventilation, proper hydration, electrolyte maintenance, and early detection were assumed responsible for the positive outcome. Medication errors are common with pediatric inpatients, and efforts to reduce them are needed.