The efficacy of continuous and intermittent nitroglycerin patches (10 mg/day) was compared in a randomized, placebo-controlled trial in 36 patients with stable angina and reproducible, exercise-induced ST depression. Intermittent treatment was administered either 18 or 14 h/day with an intermission of 6 h or 10 h, respectively. Exercise tests were performed during the last 2 h of patch application. Compared with placebo, neither continuous nitroglycerin nor the two intermittent regimens prolonged total treadmill time or time to 1 mm ST depression. No treatment eliminated exercise-induced ST depression in greater than 1 of the 36 patients. Time to angina was prolonged (by 40 +/- 66 s) only during the "10 h off" treatment (p = 0.001); time to angina increased by greater than or equal to 20% in 13 patients. Responders to treatment could be predicted by a short history of angina (p less than 0.05) and a time to angina less than or equal to 250 s during the placebo test. For each treatment, greater than or equal to 25 of the patients reported headache; 4 additional patients dropped out because of severe headache and 2 others because of a coronary event in a washout period. Thus, in most patients with stable angina, side effects outweight any benefit demonstrable with this therapy.