Eight studies that examined the relation between snoring and vascular disease were identified. The prevalence of habitual snoring, measured by questionnaire or interview, varied from 3% to 29% of adults and was dependent on age, sex, obesity, and smoking habit. In men, habitual snoring was associated with hypertension and ischaemic heart disease, with adjusted relative risks in the range 1.3-2.0. For women, only one study provided adjusted estimates of relative risk, which were 2.8 for hypertension and 1.2 for angina. Adequately adjusted relative risks for cerebrovascular disease have not been reported, but unadjusted estimates varied from 1.6 to 10.3. These studies had several limitations, including the lack of a standard definition of snoring, the use of unvalidated questionnaires, and failure to account for confounding variables and the possibility of reporting bias. Only one study was prospective. Epidemiological criteria for a causal association between snoring and vascular disease have not been satisfied. The apparent excess risk is probably due to the consequences of sleep apnoea rather than snoring itself.