The Executive Board: is made up of The President, two Executive Vice-Presidents, The General Secretary-Treasurer and the Editor.

The National Representatives: Each country is entitled to one National Representative for every 50 members (a fraction counts for one representative). If a country has less than 10 members the International Committee can decide if that country may have a representative or not. The members of each country may choose their national representative(s) before each Congress but if they do not the Executive Board is empowered to do so. The Executive Board is also empowered to choose an ad hoc representative for a country, from the members present at the Congress, if a representative is unable to be present. A list of current National Representatives is available here.

The International Committee: consists of the Executive Board, the National Representatives and one representative from each affiliated organisation. A meeting of the International Committee is held before each General Assembly.

The General Assembly: meets at the beginning and end of each Congress. All Ordinary Members, Honorary Members, Life Members, Emeritus Members, Student Members and representatives of Associate Members attending a Congress constitute a General Assembly. The General Assembly decides on matters presented to it by the International Committee and on matters raised by any member. The decision is by simple majority vote.