Objective: To compare the efficacy and tolerability of the very-low-dose perindopril 2 mg/indapamide 0.625 mg (P/I) combination with the angiotensin II antagonist losartan 50 mg (L50) in the treatment of essential hypertension. Design and methods: This was a randomized, double-blind, parallel-group study. After a 2-week placebo period, all patients included were randomized to receive either P/I or L50 for a period of 12 weeks. Patients were 18 years of age or older and required a causal measurement of supine systolic blood pressure (sSBP) between 160 and 209 mm Hg and/or supine diastolic blood pressure (sDBP) between 95 and 114 mm Hg to be enrolled in the study. A 24-h ABPM (4 measurements per hour) was performed at week 0 and week 12. Statistical analyses: To demonstrate the non inferiority of the P/I combination on causal BP measurement (sSBP and/or sDBP), minimal equivalence was tested using a one-sided test procedure with a value of P < 0.025 (per-protocol analysis). Responder and normalization rates in the two groups were compared by a chi2 test and ABPM data by a Student t test. Safety data were analyzed on all randomized patients. A value of P < 0.05 was considered significant. Results: Among the 277 patients randomized, 232 took part in per-protocol analysis (122 P/I; 110 L50). Demographic, clinical, and laboratory characteristics were comparable between the two groups at inclusion. Blood-pressure-lowering effects (casual measurement) were equivalent in the two treatment groups. The average decreases in sSBP were 21.9 ± 13.3 mm Hg for P/I and 19.8 ± 16.1 mm Hg for L50 (CI: -5.95, +8) (non inferiority P = 0.0001), and in sDBP were 14.8 ± 8.5 mm Hg for P/I and 12.9 ± 8.6 mm Hg for L50 (CI: -4.07; +8) (non inferiority P = 0.029). Responder rate (BP < 140/90 mm Hg and/or a decrease in sDBP =10 mm Hg and/or a decrease in sSBP =20 mm Hg) was significantly higher in the P/I group (91.0%) than in the L50 group (81.8%), with P = 0.04. Normalization rate (sDBP < 90 mm Hg) was also significantly in favor of the P/I group (75.4% [P/I] versus 60.0% [L50], P = 0.012). The average nighttime SBP decrease (ABPM) analyzed in 137 patients (74 P/I and 63 L50) was significantly greater in the P/I group (-10.8 ± 10.8 mm Hg [P/I] versus -7.5 ± 11.7 mm Hg [L50], P = 0.045). The rate of patients with at least one emergent adverse event was similar in the two groups. Emergent adverse events related to treatment (with a frequency >0.7%) corresponding to one patient per group only included cough (4.1% in P/I), dizziness/giddiness (1.5% in L50), and asthenia (1.4% in P/I and 1.5% in L50). Conclusion: The very-low-dose perindopril 2 mg/indapamide 0.625 mg combination gives higher response and normalization rates than losartan 50 mg. This very-low-dose combination also provides a higher nocturnal decline in SBP (ABPM), which is a major significant predictor of cardiovascular complications. Both treatments were confirmed to have good and comparable tolerability.