Former studies have demonstrated an association between habitual snoring and cardiovascular morbidity and mortality. Control for the influence of potential confounders has been inadequate. To further elucidate the issue, we examined the association between snoring and future risk of ischemic heart disease (IHD) while controlling for a number of major cardiovascular risk factors and potential effect modifiers. Some 2,937 men without overt cardiovascular disease, aged 54 to 74 y (mean = 63 years), were classified according to snoring habits and followed up prospectively during 6 years (1985 to 1991). Potential cardiovascular disease risk factors included in the study were as follows: smoking, alcohol consumption, physical activity, hypertension, blood pressure, body mass index (BMI) (kg x m-2), social class, and serum concentrations of selenium, cotinine, total cholesterol, high-density lipoprotein cholesterol, and triglycerides. During the 6-year follow-up period, 182 men (6.2%) had an IHD event (42 were fatal), and 274 men died from all causes (9.3%). There was no difference in the prevalence of snorers among those who had an IHD event and those who did not during the follow-up period, 49.9% vs 50.5%, respectively. Among the younger half of the cohort (54 to 63 years), the age-adjusted incidence of IHD was slightly but not significantly increased in snorers, relative risk (RR) = 1.2 (0.8 to 1.9). When adjustments were made for relevant confounders--use of tobacco, alcohol consumption, and BMI--the RR dropped to 1.0 (0.6 to 1.6). Among the older half (64 to 74 years), there was no increased risk in snorers, RR = 1.0 (0.7 to 1.6). We conclude that there was a slightly increased risk that did not reach statistical significance of IHD in snorers. After multivariate adjustment, snoring was not associated with risk of IHD in middle-aged and elderly men.