There are 204 current NOCs (National Olympic Committees) within the Olympic Movement. The following tables show the currently used code for each NOC and any different codes used in past Games, per the official reports from those Games. Some of the past code usage is further explained in the following sections. Codes used specifically for a Summer Games only or a Winter Games only, within the same year, are indicated by "S" and "W" respectively.
Two other significant code changes have occurred, both because of a change in the nation's designation as used by the IOC:
HOL was changed to NED for the Netherlands for the 1992 Games, reflecting the change in designation from Holland.
IRN was changed to IRI for Iran for the 1992 Games, reflecting the change in designation to Islamic Republic of Iran.
ANZ is now used in the IOC's medal database to identify the team from Australasia, composed of athletes from both Australia and New Zealand for the 1908 and 1912 Games. By 1920, both nations competed separately.
EUA is now used in the IOC's medal database to identify the Unified Team of Germany, composed of athletes representing the NOCs of both East Germany and West Germany for the 1956–1964 Games. At the time, the team was simply known as Germany in the official reports for those six Games.
EUN was used in 1992 (both Summer and Winter Games) for the Unified Team, composed of athletes from most of the ex-republics of the Soviet Union. Only the Baltic states were able to compete as independent teams in 1992; the other twelve new nations competed independently for the first time in 1994 and/or 1996.
ZZX is used to identify medals won by mixed teams of athletes from multiple nations (such as the combination of France and Great Britain, for example), a situation that happened several times in the Games of 1896, 1900, and 1904.