A 57-year-old man, previously well except for dental caries and a history of Wolff-Parkinson-White syndrome, presented with marching right-sided motor seizures of sudden onset. Cerebral arteriography and scan demonstrated an avascular left frontal lobe mass. At operation, it was identified as an abscess and was totally excised. Histologically, granules resembling those seen in actinomycosis were demonstrated in the abscess wall, but special stains revealed gram-positive cocci in chains within and outside the granules. Fungal spores, mycelia, or branching filamentous structures were absent. Acid-fast stains were negative, and alpha-hemolytic streptococcus was recovered in pure culture from the abscess. While the patient was convalescing with penicillin therapy, a dental survey revealed the presence of periodontal abscesses which were drained by exodontia. Culture of the tooth sockets showed alpha-hemolytic streptococcus and Staphylococcus aureus. The literature on this relatively rare bacterial disease which histologically resembles actinomycosis is reviewed.