Aim of this study was to determine the long term prognostic significance of maintained Thallium-201 uptake in patients with ischemic left ventricular dysfunction. We retrospectively analized 161 patients with angiographically documented coronary artery disease and reduced ejection fraction (0.35 +/- 0.9) studied by Thallium-201 viability imaging (reinjection, late redistribution or rest studies). Thallium-201 uptake was quantified in 13 segments using normalized angular profiles and a viability cut-off of 54% of the peak; regional wall motion was assessed in the same segments using echocardiography. Average follow-up was 65 +/- 50 months. Fifty-five/85 patients with dysfunctioning, mostly viable myocardium (> 50% of dysfunctioning segments) who did not undergo revascularization were more likely to experience hard events such as reinfarction (3 patients) or death (4 patients) when compared to the 30 successfully revascularized patients (1 death, no infarction). No significative difference was found between patients with dominance of cell death treated medically (76 patients) or revascularized (17 patients). These results suggest that Thallium-201 viability imaging appears to identify patients at increased risk of having reinfarction or death that have the most benefit from a revascularization procedure. Beyond short-term results, tissue viability as detected by Thallium-201 may provide important prognostic information guiding the management of patients with ischemically compromised myocardium.