This randomised trial will clearly identify whether a low-sodium, high-potassium salt-substitute is a feasible means of lowering blood pressure in high-risk individuals in rural China. The randomised design and the large size (n=600) will ensure that the results are reliable and precise. The 12-month duration will address the long-term practicability of the intervention strategy. The study is being conducted because salt-substitute-based blood pressure lowering may be particularly appropriate for rural populations in low- and middle-income countries. First, sodium intake is often very high. Second, the salt-substitute can be easily incorporated into the diet because most food is prepared and eaten at home. Third, the intervention can be provided at very low cost.