An 8-month-old male infant was treated with topical silver sulfadiazine for a burn and complicating toxic epidermal necrolysis involving 78% of his total body surface area. Transdermal absorption of propylene glycol from the silver sulfadiazine produced hyperosmolality with an increased osmolal gap. A peak propylene glycol concentration of 1,059 mg/dL was documented, and its osmotic effect was that predicted from its concentration. Our data support either zero-order elimination at a rate of 13.5 mg/dL/hr or first-order elimination with a half-life of 16.9 hours. Elevated concentrations of propylene glycol may have contributed to the patient's cardiorespiratory arrest. The osmolal gap may be used as a screen for suspected propylene glycol intoxication in selected clinical settings.