Criteria defined by von Reyn were applied to 86 cases of bacterial endocarditis. Neurologic complications (NC) were categorized according to Pruitt definitions. Neurologic accidents were observed in 48 cases. They were the first clinical manifestation in 20 patients. Neurologic events were of poor prognosis in BE, mortality increasing from 26% in patients without NC to 83% in patients with NC (P less than 0.01). Two factors affect the incidence of NC: first, the location of endocarditis with 76% of NC in mitral valve endocarditis compared with 37% in other cases (P less than 0.005); and second the infecting organism: 71% of NC in staphylococcus aureus endocarditis versus 45% in endocarditis with other bacteria (P less than 0.02). Cerebral embolism was the most common NC (25 cases) related to an occlusion of the middle cerebral artery in 21 cases with a fatal outcome in 19 patients. Other NC included 15 intracranial hemorrhages with the evidence of an aneurysm in 4 cases, 6 septic meningitis, 2 macroscopic abscesses, and 2 multiple microscopic abscesses. This study emphasizes the high rate and severity of NC in staphylococcal mitral endocarditis despite antibiotic therapy and supports early surgery in this group of bacterial endocarditis.