A multicenter study of doxazosin in the treatment of patients with mild or moderate essential hypertension and concomitant intermittent claudication. This study assessed the efficacy and safety of once-daily doxazosin in the treatment of patients (n = 19) with mild or moderate essential hypertension (sitting diastolic blood pressure [DBP] 95 to 114 mm Hg) and concomitant intermittent claudication (Doppler ankle/arm ratio of less than 0.80 and walking tolerance of less than 700 m on the treadmill). After 14 weeks of treatment with doxazosin, a significant (p less than 0.05) reduction in systolic blood pressure and DBP was observed. Mean blood pressures were reduced from 170/100 mm Hg at baseline to 161/93 mm Hg at the end of treatment. Minor changes in heart rate occurred, which with continued treatment were not statistically significant from baseline. In 12 of 16 (75.0%) efficacy-evaluable patients blood pressure was normalized (DBP to less than or equal to 90 mm Hg with an greater than or equal to 5 mm Hg reduction from baseline) with a mean daily dose of 7.6 mg/day. Doxazosin improved the hypertension severity category in 13 of 16 (81.3%) patients. The blood pressure ratios between both the thighs and arms and ankles and arms showed no statistically significant changes after treatment with doxazosin. Thigh blood flow at rest and the reactive hyperemia after 3 minutes of arterial occlusion did not change statistically. There was a tendency for pain-free distance to improve. Laboratory data were not significantly changed after treatment with doxazosin. Of the 19 patients studied, 5 reported mild or moderate side effects that were either tolerated or disappeared with continued treatment. No patient had therapy withdrawn and no patient required a dose reduction. 