Reye's syndrome (RS) is a biphasic illness that occurs predominately in children and adolescents. A prodromal viral illness (frequently influenza A or B or chicken pox) is followed by protracted vomiting and neurologic changes that start 3 to 5 days later, just when the child seems to be recovering. Aspirin has been identified as one factor contributing to the metabolic disorder that occurs. Since 1986 the FDA has required labels on all aspirin products warning about the association of aspirin use and RS. Media messages heightened public awareness regarding the alternatives to aspirin for analgesia and antipyretic use. Since 1988, the incidence of RS has decreased dramatically. RS is now more prevalent in older adolescents who may self-medicate. Because early recognition of the disease is associated with decreased morbidity and mortality, it is important for health care providers to recognize the symptoms of RS. Unexpected vomiting and disturbed brain functioning following a viral illness are symptoms of RS in children and adolescents. In infants, the symptoms of RS may be more subtle, including diarrhea, respiratory disturbances, and seizures.