Preliminary results are reported using 201Tl-myocardial scintigraphy (MSC) with quantitated analysis of redistribution kinetics immediately after ergometry (climbing step test) two to four hours later respectively and (Dual-ROI-) Equilibrium-Radionuclide-Ventriculography (ERNVG) with 99mTc-in vivo-labeled erythrocytes during bicycle exercise prior to and after nonoperative transluminal angioplasty (TAP) in nine patients with critical coronary artery stenosis. ERNVG showed a good reproducibility (r = 0,972, n:20 double check) of LVEF. Successful TAP was associated with 1. increase of LVEF from 41,8 (before) to 49,8% (after TAP), 2. increase of mean normalized systolic ejection rate (MNSER = LVEF/ET) from 1,30 (before TAP) to 1,66 (after TAP), 3. increase of maximal volume change during systole (dV/dtmax/EDV) from 2,12 (before TAP) to 3,03 s-1 (after TAP). Parameters of 201Tl-redistribution kinetics (in MSC) were normalized. Ischemic reaction index increased from 62,9 +/- 5,5 (before) to 79,1 +/- 6,9% (after TAP). The degree of 201Tl-redistribution was normalized from 10,3 +/- 7,4 (before TAP) to 2,1 +/- 1,9 (after TAP, between three and four hours after exercise) as a sign of disappearance of exercise-inducible regional myocardia ischemia after successful TAP. These preliminary results underline the effectiveness of non-operative TAP in selected cases of critical coronary artery stenosis.