The Commission on Powder Diffraction was established at the Perth Congress in 1987, with the following terms of reference:

Approved by action of the IUCr General Assembly, 25 August 2005

The Commission on High Pressure was established at the Seattle General Assembly in 1996. The following are its Terms of Reference.

At the Montreal Congress in 1957 the Commission on Electron Diffraction was established, with the following terms of reference:

The Commission on Diffraction Microstructure Imaging was established at the Prague General Assembly in August 2021.

The Commission on Crystallography in Art and Cultural Heritage was formed at the Osaka Congress in 2008 and is concerned with two main issues:
 

• Crystallography and symmetry in art;
• Crystallographic analysis (e.g. diffraction-based) of artworks and ancient materials.
   

The terms of reference are:
 

The Commission on Crystallographic Teaching was established at the Paris Congress in 1954, with the following terms of reference:

• To exchange information on teaching on an international scale.
• To promote publication of articles on teaching.
• To arrange for discussions on teaching under the auspices of the Union.

The Commission on Crystallographic Nomenclature was one of the original six commissions established by the First General Assembly of the IUCr in 1948. Its purpose was to advise on matters of scientific nomenclature as they pertained to the field of crystallography. Members of the Commission were originally nominated by the Adhering Bodies of the Union. Following the 5th General Assembly of 1960, membership of the Commission was restricted to certain editors of the Union ex officio.

In the following, by "crystal" is meant any solid having an essentially discrete diffraction diagram, and by "aperiodic crystal" is meant any crystal in which three dimensional lattice periodicity can be considered to be absent. As an extension, the latter term will also include those crystals in which three dimensional periodicity is too weak to describe significant correlations in the atomic configuration, but which can be properly described by crystallographic methods developed for actual aperiodic crystals.