We tried to assess the efficacy of precordial exercise electrocardiography (PEE) in evaluating various antianginal drugs. PEE was performed by 18 precordial electrodes. Leads V2-V7 were recorded at their usual position and one intercostal space higher and lower. The Bruce treadmill exercise protocol was used. A positivity index (PI) was formulated as follows. The total sum of maximal ST-segment depression (ΣST⇓) × 100 was divided by the product of the number of precordial leads × minutes of exercise duration: PI=ΣST⇓ × 100/n precordial leads × min The PI was measured basally and after the administration of nitroglycerin (NTG) ointment, 7.5 mg (7 patients), propranolol (P) 20–40 mg, 3 times daily (7 patients) and nifedipine (N), 10 mg 3–4 times daily (7 patients). A significant decrease of the PI was seen with NTG (p < 0.01) and P (p < 0.05) but not with N. However, in the N group, 2 patients had a significant increase in heart frequency, with resultant exercise deterioration. The remaining 6 patients had a satisfactory response to the drug (p < 0.05). The PI is useful in assessing the antianginal efficacy of various medications. From our study it is suggested that inordinate tachycardia may negate the beneficial effect of N in some patients.