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 <.001) and correlated positively and significantly to blood pressure in the total group (P <.01). The intracellular potassium to sodium ratio tended to be lower in the hypertensive group (P <.05). Thus, the present study supports increased intracellular magnesium probably unrelated to intracellular potassium-sodium imbalance in never treated, essential hypertension. © 1990 by the American Journal of Hypertension, Ltd.