Clinical guidelines have been defined as "systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances". They are designed to evaluate and implement the ever-increasing amount of evidence and opinion on best current practice. They can assist doctors and other health care professionals in making decisions about appropriate and effective care for their patients. Depending on the level of evidence, expert knowledge based and evidence-based guidelines can be distinguished. This article reviews the methods of guideline development, the state of international guidelines in dermatology and the state of the recent German psoriasis-guideline-project.