This subgroup analysis of the Irbesartan/Hydrochlorothiazide (HCTZ) Blood Pressure Reductions in Diverse Patient Populations (INCLUSIVE) trial evaluated the efficacy and safety of irbesartan/HCTZ fixed combinations in adults with uncontrolled systolic blood pressure (SBP) (140-159 mm Hg; 130-159 mm Hg for type 2 diabetes mellitus [T2DM]) after >or=4 weeks of antihypertensive monotherapy. Treatment was sequential: placebo (4-5 weeks), HCTZ 12.5 mg (2 weeks), irbesartan/HCTZ 150/12.5 mg (8 weeks), and irbesartan/HCTZ 300/25 mg (8 weeks). In the intent-to-treat analysis, mean change from baseline (end of placebo phase) off all previous therapy to Week 18 (study end) in T2DM patients (n=227) was -18.2+/-14.1 mm Hg for SBP (primary end point; p<0.001) and -8.7+/-8.2 mm Hg for diastolic blood pressure (p<0.001). Mean SBP/diastolic blood pressure changes in patients with the metabolic syndrome (n=345) were -21.0+/-14.3/-10.4+/-8.5 mm Hg (p<0.001). Overall, 56% (95% confidence interval, 49%-62%) of T2DM and 73% (95% confidence interval, 68%-77%) of metabolic syndrome patients achieved SBP goal (<140 mm Hg; <130 mm Hg for T2DM). Goal attainment rates were significantly higher among women with the metabolic syndrome than men. Treatments appeared to be well tolerated. Irbesartan/HCTZ fixed combinations achieved SBP goals in over half of the T2DM patients and nearly three quarters of patients with the metabolic syndrome, with SBP uncontrolled on antihypertensive monotherapy.