We studied the influence of captopril, atenolol, and verapamil on serum and intraerythrocyte concentrations of magnesium and zinc in 30 normotensive control subjects (12 men and 18 women, aged 30 to 65 years, mean +/- SD 45.76 +/- 12.15 years) and 30 patients with untreated mild or moderate essential hypertension (14 men and 16 women, aged 30 to 65 years, mean +/- SD 49.50 +/- 13.58 years). Ten each of the hypertensive patients were treated with captopril, atenolol, or verapamil. Physical examination and biochemical analyses (serum Mg and Zn) were done in all participants at baseline, and in patients after 3 and 6 months of treatment. The results were compared according to a nested design with Neumann-Keuls test. We found no significant differences between controls and patients in serum and intraerythrocyte concentrations of Zn at the start of the study, although there was a significant decrease in serum Zn in patients after 3 (P < .01) and 6 months (P < .001) of treatment, regardless of the drug used. This decrease was thought to be attributable to the zincuric effect of captopril or to dietary measures, or both. Intraerythrocyte Zn was not significantly affected by antihypertensive treatment. Serum and intraerythrocyte concentrations of Mg were significantly lower (P < .001) in hypertensive than in normotensive subjects, and serum Mg in patients treated with verapamil was significantly lower (P < .05) than after treatment with captopril or atenolol. Serum Mg concentration was related directly with serum concentrations of high density lipoprotein cholesterol (r = 0.4043, P < .05). We conclude that supplementation with Mg may benefit patients with hypertension.