In recent years the development of clinical guidelines has received increasing attention from medical educators and those involved in standard setting, and has been initiated at both central and local levels. This review article outlines the current state of knowledge with regard to clinical guideline implementation in medical practice. It deals with the main aspects of the current guideline debate, such as, clinical freedom and doctor autonomy, the importance of ownership in guideline implementation, the effectiveness of guidelines in changing practice and, in particular, the strategies needed to implement clinical guidelines in general practice. Mechanisms of behavioural change that have been recognized as being important for implementation are also discussed. If implementation strategies are not treated as an integral part of the development process then clinical guidelines may fail to achieve their potential in changing clinical practice.