We undertook this study to evaluate the importance of redistribution images in thallium 201 single-photon emission computed tomography (Tl-201 SPECT) assessment of myocardial viability after acute myocardial infarction. Stress-redistribution-reinjection Tl-201 SPECT was performed in 55 consecutive patients with recent (within 1 month) acute myocardial infarction. The myocardium was divided into 16 segments and activity assessed visually with a score from 0 to 3 on stress-redistribution and stress-reinjection images. A defect was considered moderate if the stress score was 2 and severe if the stress score was 0 or 1. All moderate defects were considered viable, regardless of score on redistribution or reinjection images. Severe defects were considered viable if they were reversible (improvement of 1 score) on redistribution or reinjection images. Stress-redistribution and stress-reinjection images were visually analyzed and compared in terms of viability classification. On visual analysis, 461 segments (52%) were abnormal. One hundred eleven stress defects were moderate; of these, 28 were reversible on reinjection images only and 15 on redistribution images only. However, all of these segments were viable, regardless of the analysis chosen. Of 350 severe stress defects, 48 were reversible on reinjection and irreversible on redistribution images, and 4 were reversible on redistribution and irreversible on reinjection images. Therefore, in viability assessment, 48 segments were misclassified with stress-redistribution analysis, whereas only 4 segments were misclassified using stress-reinjection analysis. Although the usefulness of Tl-201 reinjection imaging is confirmed, redistribution images seem to be of little interest in post-myocardial infarction viability assessment.