This study investigated the efficacy and safety of several different multi-drug regimens including aliskiren, valsartan, and hydrochlorothiazide (HCTZ) in patients not adequately responsive to HCTZ as monotherapy. After 4 weeks of HCTZ treatment, patients (N=641) whose diastolic blood pressure (DBP) was ≥95 mm Hg were treated for 8 weeks with either aliskiren/valsartan/HCTZ, aliskiren/HCTZ, valsartan/HCTZ, or HCTZ alone. The primary efficacy variable was change in DBP from baseline to week 8 end point. The aliskiren/valsartan/HCTZ combination produced statistically significant additional reductions in systolic blood pressure (SBP)/DBP when compared with other groups. At week 8 end point, reductions in SBP/DBP in the respective treatment groups were 22/16, 15/11, 18/14, or 6/6 mm Hg. Aliskiren/valsartan/HCTZ produced significantly better blood pressure control (SBP/DBP <140/90 mm Hg; 66.7%) compared with other treatment groups (20.5%–48.7%). The safety profile of aliskiren/valsartan/HCTZ was similar to the 2-drug combinations, with a greater blood pressure–lowering effect in patients who had not responded to HCTZ monotherapy.