This open-label, randomised, controlled study is aimed at assessing the effect of pre-treatment with the metabolic agent trimetazidine on the degree of ischaemia during percutaneous transluminal coronary angioplasty (PTCA). Overall 44 patients with one-vessel coronary artery stenosis (> 70%) in the medial part of the left anterior descending artery were included. One group (n = 22) was pre-treated with oral trimetazidine. The other group (n = 22) was the control. All patients (n = 44) were administered aspirin and conventional treatment. All patients underwent PTCA; stents were implanted in 11 trimetazidine patients and in seven control patients. The mean ST-segment elevation during all balloon inflations was significantly lower in the trimetazidine group than in the control group (-1.66 +/- 1.50 mm vs. 3.29 +/- 1.59 mm, p = 0.001). Maximal ST-segment elevations and mean ST elevation values during sequential balloon inflations were also significantly lower with trimetazidine (p = 0.018). The mean amplitude of the T-wave alterations during all balloon inflations was significantly lower with trimetazidine (3.09 +/- 2.39 mm vs. 6.83 +/- 4.31 mm; p = 0.001). Similarly, the maximal amplitude of the T-wave alterations was 4.50 +/- 2.90 mm with trimetazidine vs. 9.25 +/- 4.97 mm in control patients (p = 0.0005). Angina and rhythm disturbances were more frequent in the control group. Time from balloon inflation to onset of angina was 50 +/- 26.2 s with trimetazidine vs. 32 +/- 15.0 s, for control group (p = 0.03). The time to pain relief after deflation was 19.3 +/- 11.4 s with trimetazidine vs. 28.2 +/- 16.8 s (p = 0.001). Trimetazidine administered a few days before PTCA appears to be a cardioprotective agent for the prevention of myocardial ischaemia.