Abstract The article describes a longitudinal study testing the hypothesis that everyday stress can aggravate angina pectoris (AP). Every weekend for 1 year, 42 patients with coronary heart disease filled out a questionnaire on perceived stress for the preceding week. They also rated AP symptoms, again for the previous week. Within-subject correlation between stress and severity of AP was quite pronounced in some subjects and resulted in a sample mean of 0.38. The distribution of correlation coefficients in the sample was significantly different from a random distribution around 0. Stress values also predicted AP in the week to come. However, this finding was no longer significant when the influence of lag 1 autocorrelations between stress values was eliminated. Our results show that the effect of everyday stress on AP is essentially immediate and that it can be quite important in some subjects.