A medical guideline (also called a clinical guideline, clinical protocol or clinical practice guideline) is a document with the aim of guiding decisions and criteria regarding diagnosis, management, and treatment in specific areas of healthcare. Such documents have been in use for thousands of years during the entire history of medicine. However, in contrast to previous approaches, which were often based on tradition or authority, modern medical guidelines are based on an examination of current evidence within the paradigm of evidence-based medicine. They usually include summarized consensus statements on best practice in healthcare. A healthcare provider is obliged to know the medical guidelines of his or her profession, and has to decide whether or not to follow the recommendations of a guideline for an individual treatment. Modern clinical guidelines identify, summarize and evaluate the highest quality evidence and most current data about prevention, diagnosis, prognosis, therapy including dosage of medications, risk/benefit and cost-effectiveness. Then they define the most important questions related to clinical practice and identify all possible decision options and their outcomes. Some guidelines contain decision or computation algorithms to be followed. Thus, they integrate the identified decision points and respective courses of action with the clinical judgment and experience of practitioners. Many guidelines place the treatment alternatives into classes to help providers in deciding which treatment to use. Additional objectives of clinical guidelines are to standardize medical care, to raise quality of care, to reduce several kinds of risk (to the patient, to the healthcare provider, to medical insurers and health plans) and to achieve the best balance between cost and medical parameters such as effectiveness, specificity, sensitivity, resolutiveness, etc. It has been demonstrated repeatedly that the use of guidelines by healthcare providers such as hospitals is an effective way of achieving the objectives listed above, although they are not the only ones. Special computer software packages known as guideline execution engines have been developed to facilitate the use of medical guidelines in concert with an electronic medical record system. The Guideline Interchange Format (GLIF) is a computer representation format for clinical guidelines that can be used with such engines. It has been found that some simple clinical practice guidelines are not routinely followed to the extent they might be. It has been found that providing a nurse or other medical assistant with a checklist of recommended procedures can result in the attending physician being reminded in a timely manner regarding procedures that might have been overlooked. Guidelines are usually produced at national or international levels by medical associations or governmental bodies, such as the US Agency for Healthcare Research and Quality. Local healthcare providers may produce their own set of guidelines or adapt them from existing top-level guidelines. The USA and other countries maintain medical guideline clearinghouses. In the USA, the National Guideline Clearinghouse maintains a catalog of high-quality guidelines published by various organizations (mostly professional physician organizations) . In the United Kingdom, clinical practice guidelines are published primarily by the National Institute for Health and Clinical Excellence (NICE). In The Netherlands, two bodies (CBO and NHG) publish specialist and primary care guidelines, respectively . In Germany, the German Agency for Quality in Medicine ( ZQ) coordinates a national program for disease management guidelines. All these organisations are now members of the Guidelines International Network (G-I-N), an international network of organisations and individuals involved in clinical practice guidelines. G-I-N is owner of the International Guideline Library the largest web based data base of medical guidelines worldwide – and pursue a set of activities aiming at promoting best practice and reducing duplication.