Twelve patients with stable angina and 12 patients with unstable angina underwent rest iodine-123-beta-methyl-iodophenyl-pentadecanoic acid (BMIPP), dipyridamole stress thallium scintigraphy and delayed thallium scintigraphy. In stable angina, sensitivity for detecting ischemic segments was higher in dipyridamole thallium (74%) than rest BMIPP (48%) images (p<0.05), but there was no significant difference between the 2 images in unstable angina. In unstable angina, the incidence of segments with higher defect scores on BMIPP images than on delayed thallium images and the opposite pattern was 27 and 5 (p<0.01). In stable angina, there was no difference. The mean defect score on BMIPP (6.3 +/- 5.6) was higher than that on delayed thallium scintigraphy (2.9 +/- 2.7) and it was almost the same as on the initial dipyridamole stress test (6.5 +/- 5.2). In conclusion, BMIPP scintigraphy is safer and may be as useful in detecting myocardial ischemia in patients with unstable angina as thallium scintigraphy.