Seventeen patients with a diastolic blood pressure over 90 mm Hg were recruited from a running health screening program to participate in a double blind cross-over study of magnesium supplementation (15 mmol Mg2+/day (Emgesan, Kabi Pharmacia) for 3 weeks, followed by 30 mmol Mg2+/day for another 3 weeks, finishing with 40 mmol Mg2+/day for a final 3 weeks). A significant decrease in the mean systolic blood pressure was recorded from 154.0 +/- 10.7 mm Hg to 146.1 +/- 16.9 mm Hg (P = .031) while the mean diastolic blood pressure decreased from 100.2 +/- 4.2 mm Hg to 92.0 +/- 6.6 mm Hg (P = .0001).