Data items in the GEOM and related (GEOM_ANGLE, GEOM_BOND, GEOM_CONTACT, GEOM_HBOND and GEOM_TORSION) categories record details about the molecular geometry as calculated from the contents of the ATOM, CELL and SYMMETRY data. Geometry data are therefore redundant, in that they can be calculated from other more fundamental quantities in the data block. However, they provide a check on the correctness of both sets of data and enable the most important geometric data to be identified for publication by setting the appropriate publication flag.