90 patients on medication for mild hypertension were randomly allocated to diet and control groups and kept under surveillance by their own doctors every 2 weeks for 12 weeks to test the short-term effectiveness of a diet free from sodium additives as an alternative to medication. Mean urinary sodium excretion was reduced 37.0 mmol/24 h in the diet group and 161.0 mmol/24 h in the control group, with average K/Na ratios of 3.9 and 0.50. Both groups had a fall in mean systolic and diastolic blood pressure, but the diet group finished on half of the initial amount of medication, with 1 patient in 3 off medication and 4 out of 5 having either stopped or reduced the dose. The control group remained on almost the full amount of medication, with 2 patients out of 3 having made no reduction. The diet group had a mean weight loss of 2.1 kg, a rise in serum potassium, and a fall in serum bicarbonate. There was no increase in overall frequency of muscle cramp, and the diet group reported feeling happier, less depressed, and less dependent on analgesics. Two-thirds of the diet group intend to continue to diet indefinitely. Reduction of sodium intake permitted drug treatment to be substantially reduced without side-effects or loss of blood-pressure control.