In a double-blind, within-patient, randomized, placebo-controlled, acute study, the effects at rest and on exercise capacity of two doses of a new transdermal therapeutic system (TTS), releasing respectively 10 and 20 mg of nitroglycerin (NTG) over 24 hours, were assessed in 15 outpatients with stable exercise-induced angina pectoris. A symptom-limited exercise test was performed 4 and 24 hours after the application of each system. In comparison with placebo, both TTS-NTG doses induced a statistically significant (p less than 0.01) increase in total duration of exercise, in exercise duration to 1 mm ST segment depression, in maximal workload and in total work performed, at both 4 and 24 hours after dosing. Furthermore, both TTS-NTG doses induced a significant rise in the pressure-rate product, both 4 and 24 hours after dosing (p less than 0.01 and p less than 0.05, respectively). No statistical difference was found between the two doses of active drug in any of the above-mentioned evaluation parameters. The only unpleasant side effect was the typical nitrate headache, which occurred in 11 of 15 patients. In conclusion, a single application of TTS-NTG, 20 cm2 or 40 cm2, may improve exercise capacity over a 24-hour period in patients with stable exercise angina due to atherosclerotic heart disease.