This volume is the fifth c1assified bibliography of organic and organometallic crystal structures prepared by the Crystallographic Data Centre, University Chemical Laboratory, Cambridge, and püblished jointly with the International Union of Crystallography. The first four volumes covered the years 1935-1972. The present volume provides references principally to compounds whose structures were reported in the literature during 1972-1973. A few structures published prior to 1972 and omitted from the previous volumes are also included. The arrangement of entries in the 86 chemical c1asses is identical with the previous volumes and the reader is referred to the r ntroduction in Vol. I or Vol. 2 for a description of the practical use of the bibliography. There are three cumulative indexes in the present volume: formula, transition metal and author indexes. All three cover the period 1935- 1973 and give references to entries in Vois. 1-5. The bibliography and indexes were prepared, checked and printed by computer techniques described in the previous volumes. Magnetic tapes of the five volumes are available and anyone interested should contact the Centre for further details. Cn the present volume we have continued the special arrangement for literature search with the Centre National de la Recherche Scientifique, Paris, France. U nder this arrangement reprints of papers containing crystallographic data are sent directly to the Crystal­ lographic Data Centre, Cambridge, at the same time as they are sent out to abstractors preparing material for the Bulletin Signaletique.