The members of the Union are its Adhering Bodies.

Each Adhering Body forms a National Committee for Crystallography to represent it in the Union. 

Adherence to the Union is in one of the five Categories I-V with corresponding voting powers and contributions.

Regional Associates of the Union are organizations of crystallographers having substantially the same aims and objects as the Union.

Scientific Associates of the Union are international scientific organizations whose interests overlap with the aims and activities of the Union.

Notes for Countries Wishing to Apply for Membership of the IUCr

In order to apply for membership applicants will need to specify:

(1) the Adhering Body, which undertakes to pay the subscription (for example, an Adhering Body may be a National Academy of Science, a National Crystallographic Association or other scientific institution);

(2) the membership of the National Committee for Crystallography, including its Chair and Secretary (there is no fixed size but typically comprises 3–10 members);

(3) the category of adherence (see below).

Additionally, in order for the Executive Committee to review the application before making its recommendation to the General Assembly:

·      Applications should be received 14 months before the date of the General Assembly at which the application will be considered.  [The General Assembly determines the date and place of the next but one ordinary meeting of the General Assembly.]

·      The application should include an estimate of the number of crystallographers within the country and the number of groups represented.  Crystallographers in the country should have an entry in the World Database of Crystallographers (  

Category of Adherence

There are five Categories of Adherence with different voting rights and subscription fees.
Category of Adherence Number of Votes Annual Subscription (Swiss Francs)
I 1 1,000
II 2 3,000
III 3 6,000
IV 4 10,000
V 5 15,000