Background: Hypertension-related diseases are the leading cause of morbidity and mortality in industrially developed societies. Although antihypertensive drugs are extensively used, dietary and lifestyle modifications also are effective in the treatment of patients with hypertension. One such lifestyle intervention is the use of medically supervised, water-only fasting as a safe and effective means of normalizing blood pressure and initiating health-promoting behavioral changes. Methods: One hundred seventy-four consecutive hypertensive patients with blood pressure in excess of 140 mm Hg systolic, 90 mm Hg diastolic (140/90 mm Hg), or both were treated in an inpatient setting under medical supervision. The treatment program consisted of a short prefasting period (approximately 2 to 3 days on average) during which food consumption was limited to fruits and vegetables, followed by medically supervised water-only fasting (approximately 10 to 11 days on average) and a refeeding period (approximately 6 to 7 days on average) introducing a low-fat, low-sodium, vegan diet. Results: Almost 90% of the subjects achieved blood pressure less than 140/90 mm Hg by the end of the treatment program. The average reduction in blood pressure was 37/13 mm Hg, with the greatest decrease being observed for subjects with the most severe hypertension. Patients with stage 3 hypertension (those with systolic blood pressure greater than 180 mg Hg, diastolic blood pressure greater than 110 mg Hg, or both) had an average reduction of 60/17 mm Hg at the conclusion of treatment. All of the subjects who were taking antihypertensive medication at entry (6.3% of the total sample) successfully discontinued the use of medication. Conclusion: Medically supervised water-only fasting appears to be a safe and effective means of normalizing blood pressure and may assist in motivating health-promoting diet and lifestyle changes. (J Manipulative Physiol Ther 2001;24:335-9)