Although aminophylline and ampicillin have completely different pharmacologic properties, both are employed in the treatment of certain respiratory illnesses such as bronchial asthma. The following case report involves an accidental aminophylline intoxication subsequent to an order for ampicillin being mistaken for aminophylline. Aminophylline blood levels were quantitatively determined during the hospitalization. CASE REPORT A 4-year-old female child weighing 17 kg, with a 24-hour history of croup-like symptoms, was admitted to a local hospital. She was febrile (39.2C) and listless with labored respirations and wheezing. The patient was placed in oxygen and mist and an order was written for ampicillin, 500 mg intramuscularly immediately, and 250 mg intramuscularly every six hours.