Clinical practice guidelines can be used to achieve optimal utilization of scarce resources for the medical management of defined patient groups. However, this does not mean that the total amount of resources allocated to these patient groups will be reduced automatically. Examples of different health economic consequences for guideline implementation will be discussed, especially with regards to the cost-effectiveness to therapy and to the total health care budget. The procedural steps for developing evidence-based practice guidelines are described and the cost for their development is estimated. For Germany, the amount of this cost is about 400,000 to 500,000 DM per practice guideline. The development of evidence-based guidelines without accounting for cost-effectiveness of therapy is not reasonable as cost-effectiveness is implied in the definition of guideline objectives. Practice guidelines that are not taking into consideration health economic data may diminish the cost-benefit relation of therapy. Quality criteria of sound evidence-based guidelines are introduced. Evidence-based guidelines that are developed in cooperation with recognized clinical experts attain wide acceptance among physicians. Sound evidence-based guidelines comprising cost-benefit relations of therapy can be the core of an internal health care reform.