The coronary-arteriographic and pathologic findings in a case of Prinzmetal's angina are reported. Right coronary arteriograms performed in the absence of pain showed only minor stenotic changes, whereas those performed during an anginal attack revealed a spastic occlusion involving almost the entire vessel. Anatomic examination revealed obstructive lesions of the right coronary artery, more pronounced at the site where spasm had started, due to concentric atherosclerotic thickening of the inner wall, whereas the elastic fibers and the muscular ring of the tunica media were preserved. These findings suggest (1) the need for great caution before assuming on purely angiographic bases that spasm may affect a normal coronary artery and (2) the possibility that spasm occurs in a markedly diseased and stenotic segment of a coronary artery as long as the contractile tissue of the tunica media is preserved.