Aim of this study was to evaluate the efficacy of 2 different schedules of nitroglycerin (N), given by means of transdermal therapeutic system (TTS): continuous (20 mg patch at 8.00 am and at 8.00 pm NTTS/c) and high/low doses therapy (20 mg patch at 8.00 am and 10 mg at 8.00 pm NTTS/a), respectively. Eighteen volunteers, gave informed, written consent; male patients, aged 57 +/- 2 years, with stable effort angina pectoris, were randomly given, in double-blind condition, NTTS/c, NTTS/a or placebo (PL), each for 1 week period, according to a 3 x 3 latin square design. Bicycle exercise tests were performed on the first and on the last day of each period of the study, 12 hours after the last patch. NTTS/c and NTTS/a increased ischemic threshold and decreased the ischemic depression ST at maximal common work, compared to placebo, without differences between tests performed at 1 and 7 day. In conclusion, NTTS/a showed antiischemic activity after 7 days, so no tolerance was observed in those patients.