Abstract-Ginseng is consumed by 10% to 20% of adults in Asia and by up to 5% in Western countries. Despite observational evidence suggesting a link between its intake and the development of hypertension, there remains no long-term scrutiny for its effect on blood pressure (BP). We therefore undertook a randomized, placebo-controlled, double-blinded, crossover trial in 52 hypertensive individuals to determine the effect of 12-week North American ginseng intake on 24-hour BP; we also measured serum cystatin C as a marker of renal function. After a 4-week placebo run-in, we randomly assigned 52 participants to 3 g/day of ginseng or placebo for 12 weeks. This was followed by an 8-week washout and a subsequent 12-week period in which the opposite treatment was administered. At run-in and at weeks 0 and 12 of each treatment period, participants were fitted with an ambulatory BP monitor to assess 24-hour BP. The primary outcome was the treatment difference at week 12 in mean 24-hour systolic BP. Secondary outcomes were treatment differences at week 12 in other ambulatory BP parameters and serum cystatin C. Forty participants (77%) completed the trial, with 3 removed from main analysis (nϭ2, antihypertensive drug changes; nϭ1, incomplete ambulatory monitoring). In the remaining 37, 12-week ginseng treatment was associated with a neutral effect on all ambulatory BP parameters compared with placebo; an intention-to-treat analysis supported this. Ginseng did not affect serum cystatin C level. Overall, long-term ginseng use had no effect on 24-hour BP and renal function in hypertensive individuals. It is also shown through randomized, controlled trials (RCTs) to improve glycemic control 2 and cognitive function. 3 In contrast, however, there is repeated mention in the medical literature that ginseng can elevate blood pressure (BP). 4 -6 This stems from an early observational study by Siegel 7 that connected the self-reported use of ginseng to the development of hypertension in 14 individuals after 3 months of use. This possibility could have widespread impact, because ginseng is used by 10% to 20% of adults in Asia 8 -10 and by up to 5% in the United States, 11 Australia,12 and parts of Europe. 13 Furthermore, given that 20% to 40% of adults in these regions are estimated to have hypertension, 14 there is potential for overlap between the prevalence of ginseng use and hypertension. Still, there remains no longterm RCT investigation of the effect of ginseng on BP, and until such evaluations are undertaken, physicians will remain greatly limited in the advice they can provide to hypertensive individuals regarding ginseng use.Although many species of ginseng exist, Panax quinquefolius, or North American ginseng (NAG), and Panax ginseng together account for the majority of ginseng consumed worldwide. Recently, we demonstrated that single 3-g doses of NAG 15 and P ginseng 16 exert neutral and lowering effects on BP, respectively, for 160 minutes after intake. In the former study, 15 the neutral effect on BP was comprehensively ...