BACKGROUND: Married individuals are at reduced risk of cardiovascular disease morbidity and mortality. Recent research indicates that impaired heart rate variability (HRV) may contribute to cardiovascular disease morbidity and mortality and has also been associated with social isolation. PURPOSE: We investigated associations between HRV and marital status in patients with suspected coronary artery disease (CAD). METHODS: Eighty-eight patients who were being investigated for suspected CAD (28 women, 60 men, mean age 61.6, 60% married) were recruited from three rapid access chest pain clinics in London. Heart rate variability was measured using 24-h electrocardiograms and analyzed using frequency and time-domain measures. RESULTS: Unmarried marital status was associated with reduced heart rate variability as indexed by both frequency and time-domain measures, independently of age, gender, beta-blocker use, depression ratings, and subsequent diagnosis of significant CAD. CONCLUSION: These findings suggest that reduced heart rate variability is associated with not being married and may contribute to the reliably observed relationship between marital status and cardiovascular disease morbidity and mortality.