Since the comparison of Billroth's and Halsted's recurrence rates after mastectomy, we have known that a relation exists between the volume of procedures and the outcome of treatment. This relation still holds major promise for improved safety of patients. The NHS needs a more systematic approach to identify volume thresholds and to ensure that they are met. This will provide a firmer foundation for evidence based assessment of service mergers, capital developments, and for informed choice by patients. In 1996, the NHS Centre for Reviews and Dissemination published a systematic review to determine for which procedures such a relation existed.1 The list included coronary artery bypass surgery, paediatric heart surgery, acute myocardial infarction, coronary angioplasty, aortic aneurysm, amputation of the lower limb, gastric surgery, cholecystectomy, intestinal operations, knee replacement, and neonatal intensive care. This review was not a meta-analysis—the studies included different groups of patients, outcome measures, and methods of categorising volumes. Moreover for some procedures the better the adjustment for case mix the weaker was the relation between volume and outcome. Consequently debate about the relationship has continued. The NHS performance indicators include league tables of death rates and other outcomes, but they do not consider any relation of volume to outcome. Although the relation …