Abstract The anti-ischemic effects of atenolol and nifedipine were compared in a randomized double-blind crossover manner in 24 patients with stable exertional angina and transient silent ischemia during ambulatory electrocardiographic (ECG) monitoring. Both atenolol and nifedipine were effective (p < 0.005) in reducing the average number and duration of transient ischemic events, but therapy with atenolol was associated with a significantly greater reduction in the mean number (p < 0.05) and duration (p < 0.01) of silent ischemic events. Analyses of the silent ischemic activity during the morning hours revealed that only therapy with atenolol produced a significant reduction in the average duration per patient (139 ± 54 vs. 1,609 ± 468 s, p < 0.01) and in the average duration of silent ischemia per event between 6 am and 12 noon (62 ± 21 vs. 208 ± 24 s, p < 0.005). There were fewer adverse experiences during therapy with atenolol. These results show that although both atenolol and nifedipine are effective in reducing silent ischemic events, treatment with atenolol is associated with significantly greater efficacy, particularly on the morning surge of silent myocardial ischemia.