The objective of this study was to compare the antihypertensive effects of 3 types of antihypertensive drug regimens between different salt intake levels. The 180 patients with mild to moderate primary hypertension participating in this randomized, controlled clinical trial were randomly allocated to a low-salt diet (LSD) group or a non-low-salt diet (NLSD) group. Each group included 3 subgroups: a losartan 100 mg subgroup, a losartan 50 mg/hydrochlorothiazide (HCTZ) 12.5 mg subgroup, and an irbesartan 150 mg/HCTZ 12.5 mg subgroup. The LSD group received a diet in which the sodium content was strictly controlled (2.3 g/day). After 2 months, the office blood pressure (BP), the 24-hour mean BP, and the morning BP were significantly reduced (P ≤ .01) in each group. No significant differences were observed between the 3 LSD subgroups (P > .05). In the NLSD group, the losartan 50 mg/HCTZ 12.5 mg subgroup, and the irbesartan 150 mg/HCTZ 12.5 mg subgroup exhibited identical antihypertensive efficacy (P > .05), and these groups were significantly different from the losartan 100 mg subgroup(P ≤ .05). The BP of the patients who received the LSD was further decreased compared with those who received the NLSD (P ≤ .05). Therefore, we concluded that this LSD exerts synergistic BP-reducing effects.