At an international conference of crystallographers held in London in July 1946 under the auspices of the X-ray Analysis Group of the Institute of Physics (Nature, 158, 260 (1946); J. Sci. Instr., 24, 1 (1947)) a committee was appointed to prepare a permanent international organisation of crystallographers. This task has now been achieved, and an International Union of Crystallography has been formed and recognized by the International Council of Scientific Unions. In the countries adhering to the Union, national crystallographic committees will be set up. Among the purposes of the new Union listed in the statutes are the promotion of international co-operation and publication, and the representation of crystallography in its relations to other sciences. The first full constitutive general assembly may be delayed for a year or two, until a full-scale international gathering becomes desirable after the meeting in 1946; but the committee charged with preparing the formation of the Union has been authorized to carry on meanwhile as the executive committee. The acting general secretary is Dr. R. C. Evans, Crystallographic Laboratory, Cavendish Laboratory, Cambridge, England, to whom all correspondence should be directed.