BACKGROUND:The HARMONY study was a randomized, controlled trial examining the efficacy of an 8-week mindfulness-based stress reduction (MBSR) program for blood pressure (BP) lowering among unmedicated stage 1 hypertensive participants. METHODS: Participants diagnosed with stage 1 hypertension based on ambulatory BP were randomized to either immediate treatment of MBSR for 8 weeks or wait-list control. Primary outcome analysis evaluated whether change in awake and 24-hour ambulatory BP from baseline to week 12 was significantly different between the 2 groups. A within-group before and after MBSR analysis was also performed. RESULTS: The study enrolled 101 adults (38% male) with baseline average 24-hour ambulatory BP of 135±7.9/82±5.8mm Hg and daytime ambulatory BP of 140±7.7/87±6.3 mmHg. At week 12, the change from baseline in 24-hour ambulatory BP was 0.4±6.7/0.0±4.9mm Hg for the immediate intervention and 0.4±7.8/-0.4±4.6mm Hg for the wait-list control. There were no significant differences between intervention and wait-list control for all ambulatory BP parameters. The secondary within-group analysis found a small reduction in BP after MBSR compared with baseline, a finding limited to female subjects in a sex analysis. CONCLUSIONS: MBSR did not lower ambulatory BP by a statistically or clinically significant amount in untreated, stage 1 hypertensive patients when compared with a wait-list control group. It leaves untested whether MBSR might be useful for lowering BP by improving adherence in treated hypertensive participants.