There have been very few complete structure determination of aromatic compounds which contain more than one benzene nucleus. Robertson has recently presented conclusive evidence that the anthracene molecule is a planar configuration of carbon atoms 1.41 A. apart. Dhar has shown that moleclule of dipheyl consists of two planar hexagons of carbon atoms of a spacing of 1.42 A. with a proable distance of 1.48 A. between the nuclei. the present paper describes the analysis of a compound containing three benzene nuclei, p -diphenylbenzene (C 18 H 14 ). No data by other investigators upon the crystal form or structure of this compound have been found. Experimental. p -diphenylbenzene, a colourless substance melting at 211°, was obtained from the Eastman Kodak Company and purified by repeated crystallization from benzene and spectroscopically pure hexane. It crystallizes from benzene in this plates and from alcohol in minute monoclinic tablets which exhibit {001}, {110} and occasionally {201} forms.