National Service Frameworks are an integral part of the government's drive to 'modernise' the NHS, intended to standardise both clinical care and the design of the services used to deliver that clinical care. This article uses evidence from qualitative case studies in three general practices to illustrate the difficulties associated with the implementation of such top-down guidelines and models of service. In these studies it was found that, while there had been little explicit activity directed at implementation overall, the National Service Framework for coronary heart disease had in general fared better than that for older people. Gunn's notion of 'perfect implementation' is used to make sense of the findings.