Previous studies have shown localized thallium-201 (201TI) defects during resting anginal episodes with ST-segment elevation. In this report, findings of201TI during spontaneous angina in 14 patients with ST-segment depression and seven with normalization of negative T waves are reported. One millicurie of201TI was injected i.v. during the ischemic episode and scintigrams were taken within 5–10 minutes and after 4 hours. One week later a new injection of201T1 in a basal state provided control scintigrams.Early scintigrams showed a regional reduction of201TI uptake in all patients With normalization of negative T waves and a close correspondence between the location of the defect and the site of the electrocardiographic changes. Conversely, scintigrams in patients with ST-segment depression showed a lesser relatively milder reduction of201TI activity in 12 and no defect in two. In these patients the defect, when present, was localized in eight and diffuse in four patients. The site of the201TI defect did not always correspond to the location of STsegment depression. Overall, 4-hour scintigrams were similar to those taken in the absence of symptoms.Heart rate and systolic blood pressure measured at the onset of the electrocardiographic changes were not significantly different from asymptomatic periods but were significantly lower than during effort-induced angina, so the defects should be related to a reduction of myocardial perfusion, as documented in variant angina, rather than to an inadequate increase of coronary blood flow.From this study, angina at rest with normalization of negative T waves appears related to localized uniform reduction of myocardial perfusion, while angina with ST-segment depression is associated with a less uniform reduction of perfusion, probably located in the subendocardial layers, in the presence of severe coronary lesions.