Decreased heart rate (HR) variability is associated with increased mortality after myocardial infarction, but the prognostic value of HR variability in patients without recent myocardial infarction and its correlation with other clinical and angiographic data have not previously been reported. In the present study, detailed clinical assessments and 24-hour ambulatory electrocardiograms were performed prospectively on 100 patients undergoing elective coronary angiography. HR variability was inversely correlated with HR (r = -0.38, p = 0.001), diabetes mellitus (r = -0.22, p = 0.025) and digoxin use (r = -0.29, p = 0.004), but not with left ventricular ejection fraction, extent of coronary artery disease or other clinical, electrocardiographic or angiographic variables. All patients were followed for 1 year. Major clinical events after initial discharge occurred in 10 patients and included 6 deaths and 4 coronary bypass operations. Left ventricular ejection fraction was the only variable that correlated with the occurrence of a clinical event (p = 0.002). Decreased HR variability and ejection fraction were the best predictors of mortality (both p less than 0.01), and the contribution of HR variability to mortality was independent of ejection fraction, extent of coronary artery disease and other variables. Furthermore, 11 patients with HR variability less than 50 ms had an 18-fold increase in mortality compared with patients with HR variability greater than 50 ms (36 vs 2%, p = 0.001). Thus, decreased HR variability is a potent independent predictor of mortality in the 12 months following elective coronary angiography in patients without recent myocardial infarction.