Weight reduction was compared with metoprolol (200 mg daily) in a randomised placebo-controlled trial of first-line treatment of mild hypertension (diastolic blood pressure 90-109 mm Hg) in 56 overweight patients aged under 55 years. After 21 weeks of follow up the weight-reduction group had lost an average of 7.4 kg. The fall in their systolic pressure of 13 mm Hg was significantly greater than that in the placebo group (7 mm Hg) but not different from that in the metoprolol group (10 mm Hg). Their fall in diastolic pressure (10 mm Hg) was greater than that in both the metoprolol (6 mm Hg) and placebo (3 mm Hg) groups. At the end of the follow-up period 50% of patients in the weight-reduction group had a diastolic pressure of less than 90 mm Hg. In the metoprolol group there was a decrease in high density lipoprotein (HDL)-cholesterol and an increase in the ratio of total to HDL-cholesterol; in the weight-reduction group there was a decrease both in total cholesterol and in the ratio of total to HDL-cholesterol. Thus in this study population weight reduction produced significant and clinically important reductions in blood pressure but not the adverse effects on plasma lipids commonly associated with antihypertensive drug therapy.