Excessive salt intake is well-known to be one of the major environmental factor not only to develop human hypertension but also to induce cardiovascular damages. On the other hand, dietary potassium supplementation exerts both anti-hypertensive and cardiovascular protective effects in salt-induced hypertension. In the earlier studies including us, it was suggested that the anti-hypertensive mechanism of dietary potassium is natriuresis and sympatho-inhibitory action. Recently, it has been clarified that salt loading increases production of reactive oxygen species (ROS) in saltsensitive hypertension model animals. Because ROS overproduction induces several disadvantages, such as insulin resistance, the peripheral and central sympathetic overactivity, and an enhanced oxidized low density lipoprotein (LDL) receptor-1, lectin-like oxidized LDL receptor (LOX-1) expression, antioxidants may prevent salt-induced hypertension and cardiovascular damages. Interestingly, some investigators have demonstrated that potassium has antioxidant effect. Indeed, dietary potassium supplementation ameliorates insulin resistance, sympathetic overactivity and LOX-1 upregulation associated with decrement of ROS production. Thus, opposite actions between salt and potassium on ROS production may play an important role of their influences on blood pressure and cardiovascular effects.