Trimetazidine (TMZ) has been shown to have anti-ischaemic properties improving exercise tolerance without haemodynamic effects. A 6-month double-blind placebo-controlled study was carried out in 20 patients, mean age 59 ± 6 years, to examine the benefit of adding 60 mg of TMZ vs placebo to the classical therapy, excluding those previously treated with calcium-antagonists, conversion enzyme inhibitors, vasodilators and antiplatelet agents. All patients had severe ischaemic cardiomyopathy, confirmed by coronary angiography; six were in NYHA class IV; 14 in NYHA class III; four had mild recurrent angina pectoris. The assessment included clinical and biological evaluation, electrocardiography (ECG), 24-h ECG monitoring, cardiac volume evaluation with chest X-ray, left ventricular fractional shortening by echocardiography, left ventricular ejection fraction by radionuclide angiography. Baseline characteristics were similar in placebo (11 patients) and TMZ (nine patients) groups. Eighteen patients (nine in each group) were followed up for 6 months. In eight patients of the placebo group, treatment had to be modified (addition of calcium antagonists: four patients, conversion enzyme inhibitors: two patients; digitalics: one patient; diuretics: one patient). In the TMZ group, digitalic therapy was withdrawn in one patient and added in one patient (P<0·01). At 6 months, all TMZ group patients were free from angina; dyspnoea was improved in all TMZ patients and in only one placebo patient (P<0·001). Ejection fraction, increased by 9·3% in the TMZ group and decreased by 15·6% in the placebo group (P<0·018), CV decreased by 7% with TMZ, increased by 4% with placebo. (P = 0·034). TMZ seems to improve clinical status; ejection fraction and cardiac volume without adverse effects in patients with severe ischaemic cardiomyopathy. © 1990 The European Society of Cardiology.