Practice guidelines are systematically developed statements to assist practitioners and patients in making decisions about appropriate health care for specific clinical circumstances. Clinical practice guidelines present statements of best practice based on a thorough evaluation of the evidence from published studies on the outcomes of treatment. In November 1989, Congress mandated the creation of the Agency for Healthcare Policy and Research (AHCPR). AHCPR was given broad responsibility for supporting research, data development, and related activities. Associated with this mandate, the National Academy of Sciences published a document indicating that guidelines are expected to enhance the quality, appropriateness, and effectiveness of health care services. Guidelines as a whole have been characterized by multiple conflicts in terminology and technique. These conflicts are notable for the confusion they create and for what they reflect about differences in values, experiences, and interest among different parties. Despite this confusion, public and private development of guidelines is growing exponentially. There are only limited means to coordinate these guidelines in order to resolve inconsistencies, fill in gaps, track applications and results, and assess the soundness of individual guidelines. Significant diversity exists in clinical practice guidelines. The inconsistency amongst guidelines arises from variations in values, tolerance for risks, preferences, expertise, and conflicts of interest. In 2000, the American Society of Interventional Pain Physicians (ASIPP) first created treatment guidelines to help practitioners. There have been 4 subsequent updates. These guidelines address the issues of systematic evaluation and ongoing care of chronic or persistent pain, and provide information about the scientific basis of recommended procedures. These guidelines are expected to increase patient compliance, dispel misconceptions among providers and patients, manage patient expectations reasonably, and form the basis of a therapeutic partnership between the patient, the provider, and payors. The ASIPP guidelines are based on evidence-based medicine (EBM). EBM is in turn based on 4 basic contingencies: the recognition of the patient's problem and the construction of a structured clinical question; the ability to efficiently and effectively search the medical literature to retrieve the best available evidence to answer the clinical question; clinical appraisal of the evidence; and integration of the evidence with all aspects of the individual patient's decision-making to determine the best clinical care of the patient. Evidence synthesis for guidelines includes the review of all relevant systematic reviews and individual articles, grading them for relevance, methodologic quality, consistency, and recommendations.