This classified bibliography of organic and organometallic crystal structures covers the period 1935-1969 and provides references to over 4,000 compounds whose structures were analysed by X-ray or neutron-diffraction methods. Volume 1 deals with general organic structures and Volume 2 with complexes, organometals and organo­ metalloids. The bibliography is the first of a new series of publications "Molecular Structures and Dimensions" prepared at the Crystallo­ graphic Data Centre, University Chemical Laboratory, Cambridge. The Centre has been supported since 1965 by the Office for Scientific and Technical Information as part of the British contribution to international data activities. The main objective of the Centre is to assemble a computer-based File containing both bibliographic information and numerical data abstracted from the literature and relevant to molecular and crystal structures, as obtained by diffraction methods. The File is designed to permit the checking of published numerical values, particularly interatomic distances and bond angles and to present published results in a variety of new ways. Contents of the File will be made available through the series "Molecular Structures and Dimensions" and also by the provision of data on magnetic tapes or discs. At present the numerical data relating to molecular dimensions are being checked and will be published, at a later date, as further volumes in this series and also as magnetic tapes. The File is being extended to cover electron diffraction in the gas phase.