The role of myocardial ischaemia in the development of late potentials (LP) on the signal-averaged ECG (SAECG) in patients with coronary artery disease (CAD) remains controversial. The aim of the study was to assess the influence of transient, scintigraphically-proven (Tc-99mMI-BI), exercise-induced ischaemia on the presence of LP in 51 pts with angiographically documented CAD. Patients were divided into 2 groups: 26 pts (mean age 53 +/- 7.7) without the history of myocardial infarction (MI) (Group I) and 25 pts (mean age 56.8 +/- 6.4) after MI (Group II). SAECG recording were performed at baseline (A) and during exercise-induced ischaemia (B). The following time-domain parameters of SAECG were analyzed: the root mean square voltage of the last 40 and 50 ms of filtered QRS (RMS40, 50), total time duration of filtered QRS (t0QRS) and time duration potentials < 40 microV (LPD). The ventricular late potentials (LP) were defined as the presence of at least two of the following criteria: tQRS > 114 ms, RMS 40 < 20 mV and LPD > 38 ms. We conclude that transient exercise-induced ischaemia increased the presence of LP in pts with CAD after MI but did not alter the arrhythmogenic substrate for LP in those without the history of MI.