A healthy 14-month-old girl received gentamicin 500 mg (56 mg/kg) intravenously as empiric therapy given fever. The overdosage was quickly recognized and the child transferred to a pediatric referral center. Two hours after administration, serum creatinine was 0.3 mg/dl, though serum gentamicin level was 89 mg/L. Hemodialysis was initiated approximately 4 h after gentamicin was given and stopped 4 h later, with a serum gentamicin level of 3.4 mg/L. Gentamicin level 4 h after completion of hemodialysis was 2.3 mg/L. Three months later, the child's serum creatinine was 0.3 mg/dl, urinalysis showed no blood or protein, and audiometry showed normal hearing bilaterally at all frequencies. This child demonstrated the highest gentamicin level recorded in a patient with normal renal function. Her case demonstrates that prompt hemodialysis in this circumstance rapidly clears gentamicin without rebound. If left untreated, long-term adverse sequellae for hearing or renal function were possible; hemodialysis may have altered these outcomes.