Lattice dynamics calculations on the cubic crystal N2O4 are described. The model assumes rigid molecules with Lennard–Jones interactions between atoms. The six parameters of the model are optimized to fit the observed zone-centre frequencies, equilibrium condition, and estimated lattice energy. The form of the calculated eigenvectors and the measured relative Raman intensities of the librational modes are used to estimate the components of the polarizability tensor for the N2O4 molecule. Dispersion curves are presented for the (100), (110), and (111) directions of the Brillouin zone, and no imaginary frequencies are encountered.