A previous trial was completed in 24 patients with coronary heart disease, randomly assigned to a group who undertook a 6-month exercise training programme (5BX/XBX) and a control (no training) group. It was shown that the patients in the training group were able to achieve during exercise a higher heart rate at ST segment depression of 0.1 mV (HR/ST threshold) and that the patients in the control group showed a reduction in the threshold as well as symptomatic deterioration; the results indicated that the training programme had resulted in a reduction in the severity of myocardial ischaemia. In the present trial 9 patients of the previous training group were followed up to examine the effect of long-term maintenance training (up to 4.5 years). The same methods were used to examine the effect of maintenance training in a further group of 8 patients with coronary heart disease, 6 of whom were on beta-blocker therapy. By the end of the study, the heart rate achieved during exercise in the 17 patients was still significantly greater (P less than 0.0004) by 12.1 +/- 2.85 beats/min (mean +/- SEM) than that at the beginning of the trial; similar results were obtained in the 6 patients on beta-blocker therapy. Therefore a maintenance exercise training programme in patients with coronary heart disease can result in a sustained improvement in the form of a reduction in the severity of myocardial ischaemia, and this can occur in patients on beta-blocker therapy.