The effects of doxazosin (alpha-1-inhibitor) and enalapril (ACE-inhibitor) on blood pressure and exercise stress test were assessed in 10 hypertensive patients (8 M, 2 F, age 58 +/- 9 years) with coronary artery disease and exertional myocardial ischemia. A single blind, cross-over, placebo controlled trial was performed. Placebo was administered for 2 periods of 2 weeks, doxazosin and enalapril for at least 3 weeks. The sequence of the active drugs was randomized and the single daily dose, obtained by titration, was 7 +/- 5 mg for doxazosin and 18 +/- 13 mg for enalapril. Blood pressure measurements and treadmill tests (Bruce protocol) were performed at the end of each period. Rest systolic and diastolic pressures after placebo were respectively 173 +/- 15 and 106 +/- 9 mmHg and were reduced to 153 +/- 11 and 93 +/- 12 mmHg (p less than 0.05) after doxazosin and to 150 +/- 24 and 93 +/- 12 mmHg (p less than 0.05) after enalapril. Total exercise time was 473 +/- 91 s after placebo and increased to 545 +/- 84 s (p less than 0.05) after doxazosin and 529 +/- 100 s (p less than 0.05) after enalapril. Time to 1 mm ST depression (ST1) was 297 +/- 102 s after placebo and increased to 414 +/- 96 s (p less than 0.05) after doxazosin and to 396 +/- 133 s (p less than 0.05) after enalapril. Double product at peak exercise and at ST1 were respectively 26.3 +/- 2.8 and 22.1 +/- 2.8 x 10(3) and remained unchanged after enalapril and doxazosin. Peak exercise diastolic blood pressure was 107 +/- 5 mmHg after placebo, was reduced to 94 +/- 15 mmHg (p less than 0.05) after doxazosin and was unchanged after enalapril (101 +/- 10 mmHg, NS). Thus, doxazosin and enalapril induced a comparable decrease of rest blood pressure and a similar increase of exercise time in hypertensive patients with exertional myocardial ischemia. Doxazosin but not enalapril reduced exercise diastolic blood pressure.