Variability in atrioventricular (AV) conduction has been described in healthy subjects, whereas data for coronary patients are lacking. This study was designed to evaluate AV conduction variability in patients with stable coronary artery disease. Beat-to-beat PR interval variability with 5-minute resting high-resolution electrocardiogram recordings was measured in 30 men (mean age 50.9 years) with effort angina pectoris and 30 age-matched men without clinically evident coronary artery disease (controls). To evaluate the degree of coronary artery disease in coronary patients, coronary angiography was performed. Coronary patients displayed significantly lower values of PR interval variability compared with control subjects (P <.001). Relative PR variability (PRPP) index, calculated as the ratio of normalized PR variability to cycle length variability, was significantly higher in coronary patients (P =.001) and did depend on the degree of coronary artery disease. We concluded that coronary artery disease is associated with decreased beat-to-beat fluctuations in AV conduction. Increased relative PR variability index suggests inhomogeneous AV conduction in stable coronary atherosclerosis.