A 48-year-old woman underwent root canal treatment of the upper left lateral incisor and lower right second premolar. Close to the conclusion of the endodontic treatment she complained about headaches. Later on, because of aggravation of her condition, with headaches, fever, malaise, weakness, and numbness of the right limbs, she was admitted to the hospital. The disease progressed to an epileptic state, with appearance of a right hemiparesis. A brain scan and carotid arteriogram revealed the presence of a mass occupying the left parietal space. Craniotomy disclosed an abscess containing yellow pus from which Streptococcus viridans was cultured. After thorough surgical cleansing of the area, removal of the bone for decompression, and treatment with ampicillin the patient improved gradually and slowly regained the mobility of her right side.