We compared the results of Tl-201 myocardial SPECT of patients with arteriosclerosis obliterans (ASO), abdominal aortic aneurysm (AAA), and Takayasu arteritis (TA), so that coronary artery disease could be evaluated in them. Twenty-three patients (ASO, 9; AAA, 8; TA, 6) had Tl-201 myocardial SPECT with stress testing, and SPECT data was assessed qualitatively and quantitatively. Qualitative analysis showed that myocardial perfusion was decreased most in patients with ASO, followed by patients with AAA, and was minimally decreased in patients with TA. Quantitative analysis indicated that segmental uptake was significantly less in four segments in ASO compared with TA, less in two segments in AAA compared with TA, and less in two segments in ASO compared with AAA. Thus patients with ASO and AAA were found to have a marked abnormality in Tl-201 myocardial SPECT, indicating that this procedure should be performed in these patients. In patients with TA, however, because of minimal abnormality in myocardial perfusion, the role of SPECT is limited.