Evidence-based medicine has highlighted examples of where clinicians' treatment decisions do not accord with 'best practice' defined by high-quality research. This has resulted in the development of implementation interventions which attempt to change professional practice, such as educational programmes and audit with feedback. As these behavioural interventions themselves require a share of the health service's finite resources, it is important to evaluate their cost-effectiveness in terms of their effect on health care and hence on health outcomes. This paper considers the economic characteristics of implementation interventions and introduces methods by which their cost-effectiveness can be estimated in advance of significant investment. The paper emphasizes that implementation interventions cannot be good value for money unless the 'good practice' for which increased utilization is considered important is itself cost-effective. Furthermore, the likelihood that an implementation strategy will be cost-effective will depend on a number of factors including its cost, its effectiveness in terms of increasing utilization of 'good practice' and the costs and benefits of 'good practice' relative to an appropriate comparator.