Chronic infectious diseases may increase the risk of stroke. We investigated whether periodontal disease was a risk factor for cerebral ischemia. A case-control study with 444 stroke patients, 194 hemorrhagic patients and 250 ischemic patients, and 164 hospital controls with nonvascular and noninflammatory neurological diseases, was performed. All subjects were evaluated by either a CT scan or MRI and their number of teeth was determined. The number of teeth in the patients with cerebral ischemia was found to be significantly fewer than for the cerebral hemorrhage group and a control group between 40 and 65 years of age. The degree of tooth loss was particularly remarkable in patients with atherothrombotic and cardioembolic brain infarction. As a result, tooth loss following severe periodontal disease may therefore be a risk factor for the onset of cerebral infarction in some patients.