Congressional advisory commissions are formal groups established to provide independent advice; make recommendations for changes in public policy; study or investigate a particular problem, issue, or event; or perform a duty. While no legal definition exists for what constitutes a "congressional commission," in this report a congressional commission is defined as a multi-member independent entity that (1) is established by Congress, (2) exists temporarily, (3) serves in an advisory capacity, (4) is appointed in part or whole by Members of Congress, and (5) reports to Congress. These five characteristics differentiate a congressional commission from a presidential commission, an executive branch commission, or other bodies with "commission" in their names. Over 100 congressional commissions have been established since 1989. Throughout American history, Congress has found commissions to be useful entities in the legislative process. By establishing a commission, Congress can potentially provide a highly visible forum for important issues and assemble greater expertise than may be readily available within the legislature. Complex policy issues can be examined over a longer time period and in greater depth than may be practical for legislators. Finally, the non-partisan or bipartisan character of most congressional commissions may make their findings and recommendations more politically acceptable, both in Congress and among the public. Critics argue that many congressional commissions are expensive, often formed to take difficult decisions out of the hands of Congress, and are mostly ignored when they report their findings and recommendations. The temporary status of congressional commissions and short time period they are often given to complete their work product makes it important that legislators craft statutes creating congressional commissions with care. A wide variety of options are available, and legislators can tailor the composition, organization, and working arrangements of a commission, based on the particular goals of Congress. As a result, individual congressional commissions often have an organizational structure and powers quite different from one another. This report provides an overview and analysis of congressional advisory commissions, information on the general statutory structure of a congressional commission, and a catalog of congressional commissions created since the 101st Congress.