This study was undertaken to assess the safety and efficacy of a new long-acting formulation of diltiazem (DLA) (Cardizem LA; Biovail Pharmaceuticals, Inc., Bridgewater, NJ) in a large heterogeneous group of hypertensive patients, and to evaluate physician and patient treatment satisfaction. In this open-label, 30-day study, physicians enrolled patients with hypertension who were to be evaluated and treated at an initial visit and at 2 follow-up visits. Data recorded for each patient included demographic information, DLA dosing strength, blood pressure (BP) readings, and adverse events (AEs). A total of 15,155 physicians completed the baseline questionnaire, and 9679 (64%) completed the final clinical evaluation questionnaire. In all, 139,965 patients with hypertension were enrolled. Initial and follow-up BP data were recorded for 50,856 (36%) of these patients. On average, systolic BP (SBP) decreased from the initial visit by 10.9 mm Hg at the first follow-up (P<.0001) and by 15.5 mm Hg at the second follow-up (mean SBP, 135.7) (P<.0001). On average, diastolic BP (DBP) decreased by 6.7 mm Hg (P<.0001) and by 9.2 mm Hg (mean DBP, 79.4) (P<.0001), respectively. The most commonly reported AEs included edema, headache, dizziness, nausea, and rash; two thirds of these events were attributed to DLA. None of the AEs attributed to DLA was reported in more than 1% of patients. Both physicians and patients expressed a high degree of satisfaction with DLA. Results from this large-scale, open-label study show that DLA was safe and produced clinically meaningful reductions in SBP and DBP; in addition, a moderate to high degree of physician and patient satisfaction was reported in a large and heterogeneous cohort of patients with hypertension.