Guidelines for the management of hypertension, and those for hyperlipidaemia, advocate measurement of cholesterol in all hypertensive subjects. It is suggested that knowledge of serum cholesterol should influence the choice of anti-hypertensive agent because thiazides and beta-blockers may influence lipids adversely. However, the changes in lipids associated with low-dose thiazides and beta-blockers are small, not sustained and do not appear to affect prognosis adversely. Some believe that knowledge of serum cholesterol may help target the treatment of mild hypertension more accurately by predicting an increased risk of vascular complications of hypertension. However, serum cholesterol does not predict the risk of cardiovascular complications in hypertensive women. It does predict coronary heart disease (but not stroke) in men, but coronary risk can be estimated satisfactorily without knowledge of serum cholesterol. Suggestions that cholesterol should be lowered in hypercholesterolaemic hypertensive patients to reduce the incidence of coronary heart disease are understandable. However, the diet recommended for this has no useful effect on serum cholesterol, and the benefit of lipid-lowering drugs for cholesterol reduction only exceeds the risk in patients at very high risk of coronary mortality, for example those who have had a myocardial infarction. Hypertension alone will not place individuals at high enough risk to warrant drug therapy for cholesterol reduction. We conclude that the current guidelines are incorrect, and that routine measurement of cholesterol in all hypertensive patients is not justified.