A scattering kernel for liquid diphenyl has been determined from a model for the diphenyl molecule in which the carbon and hydrogen atoms make harmonic oscillations about their equilibrium position. The hindered translations and rotations of the molecule as a whole, which are characteristic of the liquid state, were considred as free translations of the molecule to which an effective mass was associated. A set of interatomic force constants which describes the vibrational motions of the molecule was found and then used for a complete normal-mode calculation. These force constants were calculated, using a modified least-squares technique which gives the best fit for the vibrational frequencies of the molecule measured by optical techniques. The amplitude vectors calculated from the computed set of force constants were used, together with the measured vibrational frequencies, to construct the weighted frequency spectrum used in the slow-neutron calculations. The scattering law was computed, in the harmonic approximation, by means of the code GASKET. The code FLANGE was used to interpolate the scattering law and to produce the scattering kernel. The total scattering cross section, the single differential cross section, and other neutron parameters were calculated and compared with experimental data with gratifying results.