We report here a 2-year-old boy with a Streptococcus intermedius brain abscess and bilateral ventriculitis successfully treated with a high dose penicillin G (200, 000 U/kg/dose, 6 times a day, 1 hour continuous infusion). Although hydrocephalus residued, the high dose penicillin G therapy cured his brain abscess and bilateral ventriculitis. The minimal inhibitory concentration of penicillin G to the isolate was 0.008μg/ml. The penicillin G concentration in the cerebrospinal fluid after 2 hours from the infusion was about 5μg/ml. S. intermedius must be considered as one of the causative agents for brain abscess. High dose penicillin G therapy is one choice of treatment for brain abscess due to penicillin-susceptible streptococci.