The International Union of Crystallography, inspired by pre-Second World War international co-operation between crystallographers, held its first Congress and General Assembly at Harvard University in 1948. The aims of the IUCr, as laid out in its statutes (MS. Eng. c. 5666/3), were: to promote international co-operation in crystallography; to promote the publication of crystallographic research and of crystallographic works; to facilitate the standardisation of methods and of units in crystallography; and to form a focus for the relationship of crystallography to other sciences, through the IUCr's membership of the International Council of Scientific Unions.

Hodgkin was a participant in every Congress from 1948 to 1993. At the Kyoto Congress in 1972 she was elected President of the Union, a post she held until the Amsterdam Congress three years later. As President, Hodgkin acted as chairman of the General Assembly and of the Executive Committee, as the legal representative of the Union, and as the supreme representative of the IUCr in dealing with other bodies. She served on the Executive Committee of the IUCr from 1969 until 1978, after which she was not eligible for re-election.

The bulk of the material dates from Hodgkin's Presidency and from the period that immediately followed. There is also a record of her attendance at IUCr Congresses.