Trimetazidine is a cytoprotective anti-ischaemic agent whose antianginal efficacy has been demonstrated in monotherapy versus placebo and versus reference products, and in combination with beta-blockers and nifedipine. As coprescription with diltiazem has not been previously studied, the objective of this study was to evaluate the benefit of the addition of trimetazidine (60 mg/24 h) to diltiazem (180 mg/24 h) in the stable exertional angina insufficiently improved by calcium channel blocker alone. This multicentre double-blind placebo-controlled study was conducted over a period of 6 months. The inclusion criteria were stable angina with electrically positive stress test, which remained positive despite a 15-day treatment with diltiazem (180 mg/24 h). It was conducted in 67 patients randomized into two groups: diltiazem-placebo (group I: 35 patients) and diltiazem-trimetazidine (group II: 32 patients). The follow-up consisted of clinical assessment and a stress test on inclusion and at 6 months. The two groups were similar on inclusion for all ergometric parameters, excepted for the time to onset of the ischaemic threshold of 1 mm and the total duration of effort, which were significantly longer in the placebo group. Comparison of the stress tests performed at the sixth month and on inclusion between groups I and II showed that the ischaemic threshold of 1 mm was significantly delayed by 2 minutes 41 seconds in the trimetazidine group (p < 0.001) versus 42 seconds in the placebo group (NS). Similarly, the work performed at this threshold was significantly increased by 1446 kpm in the trimetazidine group (p < 0.001) versus 564 kpm in the placebo group (p = 0.012). The difference between the two groups was significant for these two parameters, p = 0.008 and p = 0.018, respectively. At maximum effort, the total duration and the total work also increased significantly in the trimetazidine group, by 50 seconds (p = 0.006) and 570 kpm (p = 0.004), respectively, versus 16 seconds and 221 kpm in the placebo group (NS). The [double product (SBP x HR)/load (in watts)] ratio at the ischaemic threshold of 1 mm reached at M0, decreased significantly in the trimetazidine group by 69.9 (p < 0.001) versus 20.3 in the placebo group (NS). The difference between the two groups was significant (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)