The association of snoring with cerebral infarction was tested in a case-control study of 50 male patients with cerebral infarction and 100 male patients with other disorders. Cerebral infarction was significantly associated with habitual (almost always or always) snoring; the risk ratio of cerebral infarction between those who did and did not snore habitually was 10.3 (95% confidence limits 3.5-30.1). The corresponding risk ratio was 2.8 (95% CL 1.3-5.8) for snoring often, almost always, or always compared with snoring occasionally or never, but the association was still significant. The association was also found when age and body mass index were taken into account.