To assess the clinical significance of monitoring during physical training in post-myocardial infarction (MI) patients with asymptomatic exercise-induced ischaemia, we studied 232 patients who were survivors of first recent acute MI and consecutively admitted to the same CCU, who underwent an exercise test (ET) and coronary angiography within two months of the acute event. We selected the 97 patients with multivessel disease. Among them, 60 showed a negative ET and no angina; 37 showed a positive ET with significant ST segment depression, 32 of them had no angina. The 37 patients with positive ET repeated the stress test within a week. In eight of them, the two ETs differed because ischaemia was induced once with and once without precipitation of angina, while the workload (WL) and double product (DP) at the ischaemic threshold of 0.1 mV ST segment depression were not different. During a four-week training period, seven of the asymptomatic patients complained of effort angina and three of angina at rest. To assess training effects, we selected 60 non-consecutive patients with asymptomatic (38) and symptomatic (22) exercise-induced ischaemia. All the symptomatic and 25 asymptomatic patients followed a four-week physical training programme based on the ischaemic threshold. The remaining 13 asymptomatic patients did not undergo physical training. The pre-training period ergometric patterns were comparable between painful and pain-free patients. Training resulted in a similar increase in the WL at the ischaemic threshold (+45% in asymptomatic and +47% in symptomatic patients, both P less than 0.05), without any difference in the DP threshold.(ABSTRACT TRUNCATED AT 250 WORDS)