Although coronary artery disease and gastroesophageal reflux disease are common conditions which, therefore, may coexist, it is unknown whether or not the presence of one affects the other. We performed esophageal acid perfusion tests, with concurrent blood pressure, heart rate, and 12-lead electrocardiographic monitoring, in 37 patients, 25 with angiographically documented coronary disease and 12 with normal coronary arteries. Rate-pressure product, an index of myocardial work load, was calculated. In patients with coronary disease who developed chest pain during acid perfusion, rate-pressure product increased from 10.0 +/- 1.0 x 10(3) (mean +/- SEM) basally to 15.2 +/- 1.5 x 10(3) (p less than 0.001), and 3 of 9 patients showed concomitant electrocardiogram evidence of myocardial ischemia. In addition, in coronary disease, 64% of patients with infrequent or absent reflux symptoms by history had positive acid perfusion tests, and 56% of patients with coronary disease who developed pain during esophageal acid perfusion could not distinguish that pain from their usual angina. We conclude that in coronary disease, acid perfusion (and, presumably, gastroesophageal reflux) resulting in chest pain causes rate-pressure product elevation and can induce myocardial ischemia. The presence of esophageal acid sensitivity is not accurately predicted by clinical history in coronary disease, and pain of esophageal origin is often confused with angina.