This paper reports a cross-sectional survey in a defined population. The level and distribution of intraerythrocyte sodium ions (Na⁺_i) and extraerythrocyte sodium ions (Na⁺e) of 221 male and female workers were studied and their relationship with blood pressure was analysed by multiple and step-wise regression. The results suggested that: (1) A part of hypertensives and their descendents with normal blood pressure had abnormal sodium transport phenomenon in their erythrocytes membrane. (2) Plasma Na⁺ concentration was positively correlated with the blood pressure of normotensives especially those with family hypertension history. (3) The difference between Na⁺_i and Na⁺_e concentrations was negatively correlated with blood pressure (especially on SBP) of the descendents of hypertensives. (4) These effects were much greater than those produced by known factors such as sex, age, weight and height.