To evaluate the association between skeletal muscle mineral balance and effect of antihypertensive treatment, 37 patients with essential hypertension, randomly treated with either lisinopril or bendrofluazide, were investigated with skeletal muscle biopsies before and after 6 months of treatment. The ratio between calcium and magnesium concentrations in skeletal muscle prior to treatment predicted the blood pressure response during active treatment (r = -0.38, P < .02). During treatment the change in blood pressure was related to the change in muscle Ca/Mg ratio (r = 0.35, P < .05), especially in the patients treated with lisinopril. Thus, an association between the calcium and magnesium balance in skeletal muscle and the blood pressure response to antihypertensive treatment was found in the present study.