Hypertension is perhaps one of the most frequent forms of co-morbidity encountered by the anaesthetist. It is associated with a number of forms of target organ damage including cerebrovascular disease, hypertensive heart disease, coronary artery disease and renal impairment. If raised blood pressure is found in a patient prior to surgery further blood pressure readings should be obtained. There is little evidence to support an association between mild- and moderate hypertension (admission blood pressures of up to 180 mmHg diastolic and/or 179 mmHg systolic) and peri-operative complications. While there is no definitive evidence for an association between higher admission blood pressures (110 mmHg diastolic or greater and/or180 mmHg systolic or greater) and peri-operative complications, patients with admission blood pressures in this range are more likely to suffer intraoperative haemodynamic lability and peri-operative myocardial ischaemia. It is recommended that anaesthesia and surgery should be deferred in such patients if practical and that further checks of the blood pressure should be made on different occasions. Because of the effects of white-coat hypertension, blood pressure measurements taken in the peri-operative period may not reflect the patient's true blood pressure. Antihypertensive treatment guided by the British Hypertension Society Guidelines should be initiated if appropriate. If anaesthesia and surgery cannot be deferred efforts should be made to maintain the blood pressure within 20 mmHg of the awake value. Finally, it may be appropriate, where indicated, to prescribe primary or secondary cardiovascular prevention prior to discharge.