Background and aims: Endothelial dysfunction, as assessed by flow mediated dilatation (FMD) is an early event in atherosclerosis and an independent predictor of cardiovascular events. The effect of potassium supplementation on endothelial function and blood pressure (BP) in the postprandial state is not known. The aim of this study was to assess endothelial function using FMD in healthy volunteers. Methods and results: Thirty-two normotensive volunteers received a meal with 36mmol potassium (High K) and a control 6mmol potassium (Low K) meal on 2 separate occasions in a randomized order. FMD and BP were measured while participants were fasting and at 30, 60, 90 and 120min after the meal. There was a postprandial decrease in FMD in both groups. FMD decreased overall less after the High K meal compared to the Low K meal (meal effect p<0.05). Both meals produced a postprandial decrease in BP at 30min which returned to baseline levels by 120min. No significant differences in BP were observed between meals. FMD and systolic BP were negatively correlated at 90 (r=-0.54-0.55, p<0.01) and 120min (r=-0.42-0.56, p<0.01) after both meals. Conclusions: A high potassium meal, which contains a similar amount of potassium as 2.5 serves of bananas, can lessen the postprandial reduction in brachial artery FMD when compared to a low potassium meal.