A single crystal of the metastable fcc phase of La was grown of sufficient volume for the study of the lattice dynamics of this phase by coherent inelastic-neutron-scattering techniques. The phonon dispersion curves have been measured along the (xi00), (xixi0), (xixixi), and (0xi1) symmetry directions at room temperature and at 10 K. The room-temperature dispersion curves are almost identical to those of ..gamma..-Ce. In particular, the T(xixixi) exhibits anomalous dispersion for xi> or approx. =0.25. The temperature dependence of all but the T(xixixi) branch is normal. The T(xixixi) branch, on the other hand, develops at low temperatures a pronounced dip at a reduced wave vector of approximately 0.42. First-principles band-structure calculations, in which the 4f states were excluded, yield a Fermi surface with a nesting feature along the (xixixi) direction and a corresponding peak in the bare susceptibility at the wave vector of the observed phonon anomaly. The room-temperature data were used to evaluate the elastic constants, the phonon density of states, and the lattice specific heat.