The International ISBN Agency is appointed by ISO as the registration authority for the ISBN system.

The main functions of the International ISBN Agency are:

• To promote, coordinate and supervise the world-wide use of the ISBN system 

• To approve the definition and structure of group agencies 

• To allocate group identifiers to group agencies 

• To advise on the establishment and functioning of group agencies 

• To advise group agencies on the allocation of international publisher identifiers 

• To publish the assigned group numbers and publishers' prefixes