The bacteriologic and clinical findings of 39 pediatric patients with intracranial abscess are presented. Twenty-three children presented with brain abscess and 16 with subdural empyema. Predisposing conditions were present in all instances. Sinusitis was present in 25 children and 4 patients each had chronic otitis media, dental abscess, and congenital heart disease. The abscess was located in the frontal area in 14 patients, parietal in 13, and temporal in 12. Anaerobic organisms alone were recovered in 22 patients (56%), aerobic bacteria alone in 7 (18%), and mixed aerobic and anaerobic bacteria in 10 (26%) patients. There were 79 anaerobic isolates (2 per specimen). The predominant anaerobes were anaerobic Gram-positive cocci (29 isolates); Bacteroides sp. (12, including 5 Bacteroides fragilis group), Fusobacterium sp. (14 isolates); and Prevotella sp. and Actinomyces sp. (6 isolates each). A total of 17 aerobic or facultative isolates (0.4 per specimen), including 11 Gram-positive cocci and 6 Haemophilus sp., were recovered. Antimicrobial therapy was administered to all patients. Nine patients (i.e., 6 with sinusitis and subdural empyema, 3 with sinusitis and brain abscess) did not respond to antimicrobial therapy and aspiration of the abscess, and required surgical drainage of inflamed sinuses. These findings indicate the major role of anaerobic organisms in the polymicrobial etiology of intracranial abscess in children.