This double-blind, placebo-controlled study sought to examine the short-term benefit of adding 60 mg of trimetazidine to the daily therapeutic regimen of 29 male patients with coronary insufficiency who had persistent ST depression on exercise tolerance test (greater than or equal to 1 mm), despite treatment with nifedipine 40 mg per day. As compared with the placebo group, after only 14 days, the patients treated with trimetazidine showed statistically significant increases in the maximum workload level attained before ST depression occurred (31% versus - 6%; P = 0.009), the total work performed (31% versus 2%; P = 0.024) and a significant decrease in the systolic tension time (double product)/workload ratio (-5% versus +11%; P = 0.005). Throughout the study the clinical acceptability was excellent, with no side effects attributable to trimetazidine being recorded. This study shows that the addition of trimetazidine to a calcium antagonist brings a valuable improvement in therapeutic results.