In the present study we aimed at evaluating the intracellular concentrations of magnesium, potassium and sodium in 50-year-old, otherwise healthy white men with never treated, essential hypertension (n = 12) and in normotensive control subjects (n = 12) matched for age, sex, race, height, weight and smoking habits. Intraerythrocyte magnesium was significantly increased in the hypertensive group (P less than .001) and correlated positively and significantly to blood pressure in the total group (P less than .01). The intracellular potassium to sodium ratio tended to be lower in the hypertensive group (P less than .05). Thus, the present study supports increased intracellular magnesium probably unrelated to intracellular potassium-sodium imbalance in never treated, essential hypertension.