['Individuals with prehypertension are at risk of hypertension and cardiovascular diseases, and yet efficient interventions are lagging behind. Studies indicate that heart rate variability-biofeedback (HRV-BF) increases HRV and baroreflex sensitivity (BRS) as well as reduces related pathological symptoms, suggesting potentially beneficial effects of HRV-BF on prehypertension, but little is known about these effects. In this study, these effects were investigated and their mechanisms were explored.', 'The effect of HRV-BF on prehypertension in young adults and its potential mechanism were explored.', 'Forty-three (43) individuals with prehypertension were recruited and classified into three categories: HRV-BF group, slow abdominal breathing group, and control group. All groups were assessed with measurements of noninvasive blood pressure (BP), BRS, respiration, and galvanic skin response (GSR) at pre-intervention, in the entire process of each session, at postintervention, as well as at a 3-month follow-up.', 'Subjects participated in a 10-session HRV-BF protocol or simple slow abdominal breathing protocol conducted over 5 weeks. A 3-month follow-up was also performed on these individuals.', 'The incidence of prehypertension was as high as 14.5% in young college students. Individuals with prehypertension were lower in BRS (7.5±5.2\u2009ms/mm Hg) and HRV (log10-transformed of the standard deviation of normal-to-normal beats [SDNN]=1.62±0.13\u2009ms, lgTotal power of spectral density in the range of frequencies between 0 and 0.4Hz (TP)=8.02±0.55\u2009ms2) than those with normal blood pressure (BRS=18.4±7.4\u2009ms/mm Hg, lgSDNN=1.79±0.10\u2009ms, lgTP=8.68±0.85\u2009ms2). HRV-BF reduced blood pressure (from 131.7±8.7/79.3±4.7\u2009mm Hg to 118.9±7.3\u2009mm Hg/71.9±4.9\u2009mm Hg, p<0.01), increased BRS (from 7.0±5.9\u2009ms/mm Hg to 15.8±5.3\u2009ms/mm Hg, p<0.01) and increased HRV (lgSDNN from 1.61±0.11 to 1.75±0.05\u2009ms, and lgTP from 8.07±0.54 to 9.08±0.41\u2009ms2, p<0.01). These effects were more obvious than those of the slow-breathing group, and remained for at least 3 months. HRV-BF also significantly increased vagus-associated HRV indices and decreased GSR (indices of sympathetic tone).'] Does heart rate variability biofeedback decrease blood pressure in prehypertensive subjects by improving autonomic function and baroreflex?