Severe hepatotoxicity in acute acetaminophen overdose in children is uncommon. This apparent protection does not extend to chronic or repeated high dose acetaminophen administration. The Illinois Poison Center (IPC) was consulted on a case involving a 7 month old 17 lb infant, who had presented the day prior to an emergency department with complaint of febrile illness. Patient had been prescribed acetaminophen for symptoms, and the mother called IPC when she realized that she had been incorrectly giving the patient concentrated infant acetaminophen (80 mg per 0.8 mL) totalling 42.3 mg/kg/dose or 234 mg/kg/24 hours instead of children's acetaminophen (160 mg/5 ml). Per recently published national triage guidelines, the patient was referred to an acute care facility for evaluation. The patient presented with significantly elevated aspartate aminotransferrase (AST) and alanine aminotransferrase (ALT) levels of 1339 and 907 U/L respectively, and was initiated on i.v. n-acetylcysteine therapy. The patient responded well to therapy, with AST and ALT declining to 145 and 479 U/L respectively over the next 48 hours. This case represents one of the shortest durations of chronic acetaminophen therapy to cause hepatic injury in an infant. Further, while the level was only slightly above the national triage guideline recommended referral dose per 24 hours, significant hepatotoxicity was observed.