There was strong circumstantial evidence relating sodium intake to hypertension. Most impressive evidence came from the study of the 'low-salt tribes', subsisting on a very low sodium intake. They failed to develop hypertension, or even gradual rise of blood pressure with age. Many studies published on the effect of lowering sodium intake on blood pressure of hypertensive patients had been positive. In one investigation, blood pressure fell approximately 9 (systolic)/6 (diastolic) mmHg when sodium intake was reduced from approximately l80 to l00 mEq/day. Reduction of sodium intake to a level of 70-l00 mEq/day appeared within the capability of most people and maintenance up to a period of two years had been indicated with minimal follow-up procedures.