Objectives This study tested the usefulness of nitrate-enhanced thallium 201 imaging for detecting myocardial viability. Background Previous work suggests that nitrates enhance the ability of ²⁰¹Tl imaging to detect viable myocardium. Methods Eighteen patients with coronary artery disease underwent ²⁰¹Tl imaging at rest, after 4 hours of redistribution, and during intravenous nitroglycerine infusion (mean dose = 5.96 ± 5.37 μg/kg/min). Twelve patients had their echocardiograms repeated after revascularization. Perfusion and wall motion were scored from 0 to 2 (absent to normal). Results All the regions identified as viable by the rest/redistribution pair of scans were identified as viable by the rest/nitroglycerine pair of scans. Ninety-one percent of these regions were identified as viable by the single nitroglycerine scan alone. In patients who underwent revascularization, the total ²⁰¹Tl perfusion score improved from 193 to 214 after revascularization (P = .009). Wall motion score improved from 151 to 168 after revascularization (P = .09). Both the rest/nitroglycerine and rest/redistribution studies correctly predicted 14 (88%) of 16 regions that improved after revascularization. Most importantly, the rest/nitroglycerine and rest/redistribution studies were able to predict postrevascularization myocardial viability (absence of akinesis or dyskinesis after revascularization), with a sensitivity of 95% and 92%, respectively, and a predictive accuracy of 84.4%. Conclusions Nitroglycerine infusion during ²⁰¹Tl imaging is a useful technique for detecting underperfused, viable myocardium, requires less time to perform than rest/redistribution imaging, and may allow detection of viable myocardium with a single ²⁰¹Tl single-photon emission computed tomographic study. (Am Heart J 1999;138:369-75.)