The antianginal effects of sustained-released oral nitroglycerin were evaluated in patients with chronic stable angina using a double-blind randomized protocol. Nineteen patients were inducted into the trial and 17 of these completed the study. Two doses of oral nitroglycerin were used; 2.6 mg and 6.5 mg given three times daily for a period of 2 weeks, the patients crossing over to the alternative dose at the end of each period. Evaluation of effect was carried out 2 hours after the morning dose using graded treadmill exercise testing with on-line computer analysis of the electrocardiogram (EKG) (CASE, Marquette Electronics, Inc.). Various exercise parameters were measured and the results compared to placebo values and between the two dosages. The aim was to demonstrate an antianginal effect and to look for a dose-response relationship and for attenuation of effect if any on continued administration. The mean±SEM exercise time on placebo was 6.7±0.6 min, increasing to 8.6±8 min (p<0.02) with="" 2.6="" mg="" tds="" dosage="" and="" 8.4±0.7="" min=""><0.01) with="" 6.5="" mg="" tds="" of="" oral="" nitroglycerin.="" none="" of="" the="" other="" exercise-derived="" indices="" were="" altered="" significantly="" by="" oral="" nitroglycerin.="" two="" patients="" were="" withdrawn="" because="" of="" severe="" headaches="" and="" both="" were="" receiving="" the="" higher="" dose.="" the="" data="" did="" not="" demonstrate="" and="" dose-response="" relationship="" but="" confirmed="" the="" anti-anginal="" efficacy="" of="" sustained="" action="" oral="" nitroglycerin.="" this="" efficacy="" did="" not="" show="" any="" significant="" attenuation="" of="" effect="" on="" continued="" administration,="" indicating="" a="" possible="" lack="" of="" development="" of="">