We report a 6-month-old female infant with status convulsivus which appeared during intravenous drip infusion of aminophylline. She had an extremely high serum theophylline concentration (79 micrograms/ml), which was effectively reduced by plasmapheresis and dialysis. Three days later, she developed status convulsivus again, though her serum theophylline was undetectable at that time. A CT on 14th day of illness revealed mild widening of frontal sulci and Sylvian fissure. The patient apparently recovered her healthy condition, but psychomotor developmental delay, especially in speech and social behavior, was noted at the age of 2 years 6 months (DQ = 55). A delay of myelination was observed on brain MRI at 4 year 1 months, suggesting an irreversible brain injury caused by theophylline intoxication.