A case is reported here of brain abscess due to Streptococcus sanguis in association with multiple pulmonary arteriovenous fistulas. A 19-year-old male who had been diagnosed in 1988 as pulmonary arteriovenous fistulas was admitted to our hospital for repeated epistaxis, headache, and vomiting. A brain abscess which was diagnosed using various roentogenologic examinations, worsened despite conservative therapy. Additional surgical drainage was performed; S. sanguis was isolated from the drainage fluid. After drainage, clinical symptoms gradually improved with no subsequent neurological deficits. We have formulated the following hypothesis regarding the mechanism of abscess formation in this case: S. sanguis invaded from a ruptured nasomucosal vein, forming a septic emboli in the blood flow, which passed through a pulmonary arteriovenous shunt and led to the formation of a brain abscess which established a metastatic presence in the cerebral tissue.