It is recognized that the development of hypertension in Dahl salt-sensitive (DS) rats as compared to Dahl salt-resistant (DR) rats is dependent on the addition of a high percentage of sodium chloride, often 8% to the diet. In this work, blood systolic pressure and the concentrations of many elements in different tissues of DS and DR rats were measured. However, to distinguish the modifications linked to the strain from the modifications owing to excess of sodium intake, no additional Na was included in the diet in all our experiments. Without any addition of sodium chloride to the diet, a statistically significant increase of the systolic blood pressure of DS rats (152 +/- 10 mmHg) in comparison to DR rats (131 +/- 3 mmHg) was observed. The analysis of the concentrations of many elements in different tissues showed no major modifications of sodium concentrations in DS rats as compared to DR rats, but a decrease of calcium in plasma (-9%), brain (-20%), and heart (-7%) and of magnesium in plasma (-13%), kidney (-11%), and bone (-7%). In conclusion, an increased intake of Na is not necessary to obtain a higher systolic blood pressure in DS rats compared to DR rats. Since we did not find noticeable modifications of Na concentration in tissues but modifications of Ca and Mg, we suggest that an alteration of the homeostasis of these two elements may be involved in the development of the hypertension in DS rats.