Matching programs were made trying to maximize the chance that residency and fellowship programs fill all available positions every year with candidates that they consider suitable; and also, the chance that an applicant gets the position that he/she considers the best according to their goals and aptitudes.

There are several matching programs running every year (San Francisco Match, Urology Match, US Military Match), but the National Residency Matching Program, or main match, is the one which IMG's and most AMG's apply to. Approximately 25.000 positions are appointed every year in the United States by the main match, 15.000 of those to AMG's and 10.000 to IMG's.