OBJECTIVES: To preliminarily assess the effects of acupuncture on prehypertension and stage I hypertension, and to provide data for further research. DESIGN: A randomized, controlled, assessor-blinded study with an 8-week intervention period and a 4-week follow-up. INTERVENTIONS: Participants were patients with systolic blood pressure (SBP) of 120-159mmHg or diastolic blood pressure (DBP) of 80-99mmHg.Thirty participants were allocated to acupuncture group or untreated control group at a 1:1 ratio. The acupuncture group received standard acupuncture twice weekly for 8 weeks, and was followed-up for 4 weeks after treatment; the control group did not receive any type of anti-hypertensive treatment for 12 weeks. MAIN OUTCOME MEASURES: Primary outcome measure was SBP and DBP at post-treatment. The secondary outcomes were SBP and DBP at follow-up; Euro Quality of life (EQ-5D), heart rate variability (HRV), body mass index (BMI), and blood lipid profile. RESULTS: DBP (-5.7mmHg; P=0.025), but not SBP (-6.0mmHg; P=0.123), was significantly different between groups at post-treatment. Both DBP (-7.8mmHg; P=0.004) and SBP (-8.6mmHg; P=0.031) were significantly different at follow-up. Among the HRV indices, only high frequency power was significantly different between groups at weeks 4 and 8 (P=0.047 and P=0.030, respectively). There were no differences between groups in EQ-5D, BMI or lipid profile. CONCLUSION: The results of this study show that acupuncture might lower blood pressure in prehypertension and stage I hypertension, and further RCT need 97 participants in each group. The effect of acupuncture on prehypertension and mild hypertension should be confirmed in larger studies. TRIAL REGISTRATION: KCT0000496.