Doxazosin, an effective treatment for mild-to-moderate hypertension and benign prostatic hyperplasia, in its standard formulation requires a multiple-step titration regimen to minimize the potential for first-dose effects. A new controlled-release gastrointestinal therapeutic system (GITS) formulation of doxazosin was developed to enhance the pharmacokinetic profile, significantly reducing serum peak-to-trough ratios, thereby minimizing the need for titration. We assessed the efficacy and tolerability of doxazosin GITS compared with doxazosin standard and placebo in a prospective, randomized, double-blind, parallel-group, dose-titration, multicenter study of 392 patients with mild hypertension (blood pressure [BP] < or = 180/95-105 mmHg). Patients were randomized to doxazosin GITS, doxazosin standard, or placebo in 2:2:1 manner. The primary outcome measure was the proportion of patients in the per-protocol analysis (PPA) who achieved goal BP response (sitting BP < or = 90 mmg or 10 mmHg decrease from baseline at 24 h postdose at the final evaluable visit). Goal BP response in the intention-to-treat (ITT) population and prespecified BP and/or heart rate changes in the PPA and/or ITT population were also analyzed. Tolerability was assessed throughout the study. Doxazosin GITS and doxazosin standard produced comparable goal BP responses superior to that of placebo, with 92 of 156 patients (59.0%) on doxazosin GITS and 86 of 152 patients (56.6%) on doxazosin standard in the PPA population achieving goal BP response 24 hours postdose on the final visit, compared with 25 of 70 patients (35.7%) on placebo. Both active treatments produced mean significant BP reductions compared with baseline and placebo (p < 0.001). The most commonly reported side effects were headache, dizziness, and asthenia. No syncope was reported in the doxazosin GITS group; two cases were observed in the doxazosin standard group and one case in the placebo group. Doxazosin GITS was well tolerated and as effective as doxazosin standard in patients with mild hypertension, producing well-tolerated, comparable BP reductions with minimal need for titration. Both active treatments were clinically and statistically superior to placebo.