In order to assess if acute ischemia induces ventricular late potentials (VLP), we have studied 35 patients during coronary angioplasty (PTCA), 15 (Group A) with previous myocardial infarction, 20 (Group B) without. VLP detection was performed by standard technique (in the time domain, with Simson algorithm, on 200 beats, using a 25 Hz filter) before, during and 24 hours after PTCA. This procedure was performed on: anterior descending artery (19 cases), circumflex artery (9 cases), right coronary artery (11 cases); four patients had PTCA on two vessels; in Group A patients, PTCA was performed in vessels related to the previous myocardial infarction. VLP were defined as present when at least two of three standard criteria of positivity were detected (QRSD > 115 ms, RMS40 < 25 microV, LPD > 32 ms). In all patients also left ventricular ejection fraction, end diastolic pressure, regional kinesis and amount of myocardium at risk (as measured by the "Duke University jeopardy score") had been assessed. Furthermore, the total and mean inflation time and the degree of induced acute ischemia were also considered. The following results were obtained: no patient had VLP at basal conditions, during PTCA in all patients of both groups we observed a significant prolongation of QRSD but only Group A patients developed VLP, in 56% of cases versus none of Group B. This event was transient: in fact, 24 hours after the procedure VLP were no more present. The two groups did not differ as regards to the values of all the other anatomic and functional above mentioned parameters. Probably the acute ischemia cannot evocate VLP by itself, but this "trigger" needs also a particular substrate with anatomical and functional abnormalities due to a previous myocardial infarction. Further investigations and long follow-up studies are requested to assess if these data could account for the presence of ventricular tachyarrhythmias in patients with acute coronary ischemia and previous myocardial infarction.