In the Training Levels Comparison Trial, 197 male coronary heart disease patients were randomized to low or high intensity training with target heart rates, which corresponded to 50% and 85% of the ˙VO2max achieved on the previous exercise test, respectively. Patients were to exercise at their assigned intensity level at three 1-h long supervised sessions per week for 2 yr. This paper reports on two components of adherence: attendance at exercise sessions and achievement of heart rates in the target range. During the first year of training, the average percent of exercise sessions attended (mean± SE) for the low intensity group (64.0% ± 2.5%) was significantly higher than for the high intensity group (55.5% ± 2.7%). At the end of 1 yr of training, 54% and 37% of the low and high intensity patients, respectively, achieved heart rates within 5 beats·min-1 of their target heart rates. Although the low intensity program was preferable to achieve maximum attendance, attenders on the high intensity program achieved higher heart rates. These results suggest that to maximize the achieved heart rate, it would be optimal to motivate a cardiac rehabilitation patient to train at the high intensity level for a prolonged period of time.