In this study we compared different dietary constituents and their effect on the angina threshold. We compared carbohydrate-rich, fat-rich and balanced liquid diets on effort tolerance in 14 patients of mean (range) 61 (41-73) years of age with chronic stable angina. On four different occasions at least 1 week apart, patients had exercise treadmill tests after an overnight fast and then after a rest period of 1 h ingested one of three different approximately isocalorific (about 4000 kJ) liquid drinks of 600 ml consisting mainly of: fat, carbohydrate or a balanced meal with an equal volume of water as control. Meals were given in random order. Analysis of the mean (SD) differences in heart rate between fasting and the post-prandial state for the different meals revealed a significant increase between water and the other meals, fat (+4(6) beats.min-1 P < 0.002), balanced (+9(17) beats.min-1 P < 0.004), and carbohydrate (+10(12) beats.min-1 P < 0.0002). There was no significant difference between the groups as regards systolic or diastolic blood pressure. Cardiac output increased following the meals but decreased after water; however, there was a significant difference between water and balanced meals. Exercise tolerance fell following all the meals but was significantly greater after a balanced (mean (SD) -108(129) s P < 0.01) and carbohydrate meal (-92(52) s P < 0.001). The reduction in exercise duration following a fat meal (-36(53)s) was not significantly different from that following water (-8(43) s) but was significantly smaller than after a carbohydrate meal (P < 0.02). Time to 1 mm of ST depression showed similar changes to that of total exercise duration, being significantly lower after a carbohydrate (mean (SD) -76(77) s P < 0.01) and balanced meal (-76(63) s P < 0.005). Time to 1 mm ST depression, although reduced by a fat meal (-15(84) s) was significantly less than after a carbohydrate meal (P < 0.02). In conclusion, patients with chronic stable angina have impaired effort tolerance and a lower angina threshold after high calorie containing liquid meals. Meals rich in carbohydrate have greater effects than meals where the majority of calories are derived from fat. Patients should be advised to avoid exercise in the first 30 min after eating.