Emotional stress has been implicated in the development and progression of coronary artery disease, with 1 proposed causal pathway being changes in cardiac autonomic tone. One hundred thirty-five patients with coronary artery disease underwent 48 hours of ambulatory electrocardiographic monitoring and completed activity and mood diaries every 20 minutes while awake. Random-effects model analyses associated higher levels of negative emotions (e.g., anger, stress, sadness) with decreases in high- and low-frequency power, whereas higher levels of positive emotion were related to an increase in low-frequency power, independent of age, posture, and medications.