Valid guidelines, when appropriately disseminated and implemented, can lead to changes in clinical practice and improvements in patient outcome. Guidelines are more likely to be valid if they are developed using systematic reviews, national or regional guideline development groups (including representatives of key disciplines) and explicit links between recommendations and scientific evidence. This paper discusses the practical implications of adopting this approach for guideline development and the role of peer review guidelines as another element of the process to ensure validity. Considerable resources are required to develop evidence-linked guidelines, but this investment can be recouped by relatively small changes in the process or outcome of care. Good leadership and technical support are required for the successful development of clinically valid guidelines, which is dependent upon the small-group processes of guideline development panels and the translation of evidence into recommendations. Future guideline developers need to gain expertise in these areas. Research priorities are identified.