The usefulness of the intravenous dipyridamole-echocardiography test (12-lead and two-dimensional [2-D] echo monitoring during dipyridamole infusion) in the diagnosis of coronary artery disease recently has been suggested. However, the intravenous form of dipyridamole is not available for clinical use in some countries and therefore the administration of oral dipyridamole has been employed in combination with echocardiography. In order to evaluate the relative usefulness of the oral (300 mg of pulverized tablets) vs the intravenous (up to 0.84 mg/kg in 10 min) dipyridamole-echocardiography test, we performed the two tests, on different days and in random order, in 28 inhospital patients: 21 had coronary artery disease (seven had one-vessel disease, eight had two-vessel disease, and six had three-vessel disease); seven patients had no significant coronary artery disease. For both tests, the diagnostic end-point was the development of a transient dyssynergy of contraction. Sensitivity was 95 percent for the intravenous and 52 percent for the oral dipyridamole-echocardiography test (p < 0.01); in positive cases, the dyssynergy after the dipyridamole administration appeared at 6.5 +/- 2.5 min for the intravenous and at 27.8 +/- 12.4 min for the oral test (p < 0.01). Specificity was 100 percent for both the intravenous and oral dipyridamole-echocardiography test. One or more extracardiac side effects (headache, gastrointestinal upset, flushing, etc) occurred in 61 percent of the intravenous and 68 percent of the oral tests (p = ns). Nine patients with a positive intravenous and oral dipyridamole-echocardiography test also had a positive exercise-electrocardiography test. A significant correlation between exercise time (ie, the time from onset of exercise and 0.1 m V of ST segment shift) and dipyridamole time (ie, the time from onset of dipyridamole administration and the development of frank dyssynergy) was present for the intravenous (r = 0.6, p < 0.05) but not for the oral test. We conclude that the oral dipyridamole-echocardiography test, in comparison with the intravenous dipyridamole-echocardiography test, has a lower sensitivity and requires a substantially longer imaging time. The dipyridamole time is related to exercise time for intravenous but not for the oral dipyridamole-echocardiography test.