This study examined the merits of oral dipyridamole SPECT thallium-201 imaging in detecting CAD and multivessel CAD. The 65 patients included in this study (aged 62 ± 11 years) were not candidates for exercise testing (for the usual reasons). Coronary arteriography revealed no significant CAD in 17 patients and ≥50% narrowing of one or more vessels in 48 patients; 12 had one-vessel and 36 had multivessel CAD (high-risk group). Thallium-201 was injected intravenously 45 minutes after an oral dose of 375 mg of dipyridamole, and SPECT imaging was performed within 10 minutes and 4 hours after injection. There were no serious side effects; only six patients (8%) had ST segment depression and 18 patients (28%) had chest pain. The heart rate increased from 74 ± 15 beats/min at rest to 84 ± 14 beats/min at peak effect (p = 0.001); the systolic blood pressure did not change (130 ± 18 and 128 ± 20 mm Hg, respectively, p = NS). The thallium images were abnormal in 6 of 17 patients (35%) with no CAD, in 7 of 12 patients with one-vessel disease (58%), and in 34 of 36 patients with multivessel CAD (94%) (p = 0.001). Twenty-one of 25 patients (84%) with a perfusion abnormality in more than one vascular territory had multivessel CAD assessed by angiography. Thus oral dipyridamole SPECT thallium-201 imaging is a safe and inexpenive method for the detection of CAD in patients who are otherwise not candidates for exercise testing. Patients with perfusion defects in more than one vascular territory are highly likely to have multivessel CAD assessed by angiography. In our experience, these results are not different from those achieved with submaximal exercise SPECT thallium-201 imaging. © 1989.