The recently developed myocardial agent methoxy-isobutyl-isonitrile (MIBI), labelled to 99mTc, allows one to evaluate global and regional ventricular function as well as myocardial perfusion by means of a single exercise stress test, significantly increasing diagnostic accuracy for coronary artery disease. Between September 1988 and March 1989, 407 patients with either suspected or already ascertained coronary artery disease underwent simultaneous assessment of regional ventricular function with first pass radionuclide angiography, and of myocardial perfusion with single photon emission computerized tomography, by means of 2 injections of 99mTc-MIBI at rest and at peak of the same exercise test. Out of these patients, 56 (52 men and 4 women, whose mean age was 57 +/- 7 years) underwent coronary angiography within 6 months of radionuclide examination and were included in the study. There were 13 1-vessel, 26 2-vessel and 17 3-vessel disease patients. Thirty-six of them had had a previous (greater than 6 months old) myocardial infarction, on the anterior wall in 16 patients, on the inferior wall in 20. In all patients a computerized bicycle stress test was performed; interruption criteria were ST segment depression greater than or equal to 1 mm in 27 patients (48%), the achievement of a heart rate greater than 85% of maximal age-predicted heart rate in 12 patients (22%) and fatigue in 17 patients (30%). Scintigraphic results were compared to angiographic findings: global sensitivity and specificity of the simultaneous evaluation were 82% and 81%, respectively, vs 95% and 56% of functional results and 85% and 71% of perfusion results, respectively. Regional analysis was also performed, by dividing scintigraphic images into the territories supplied by the 3 main coronary vessels, i.e., left anterior descending artery (LAD), left circumflex artery (LCx) and posterior descending artery (PD). On LAD territory the simultaneous evaluation achieved a sensitivity of 88% and a specificity of 63%, vs 98% and 38% of functional analysis and 88% and 50% of perfusional analysis, respectively. On LCx territory sensitivity and specificity were respectively 71% and 96%, vs 91% and 64% of function, and 77% and 96% of perfusion alone. On PD territory sensitivity was 85%, vs 94% and 91%, respectively; specificity was 73%, vs 55% and 55%, respectively. Combined functional and perfusional analysis achieved a 68% sensitivity in identifying less than or equal to 75% coronary narrowings, and a 90% sensitivity for greater than 90% narrowings.(ABSTRACT TRUNCATED AT 400 WORDS)