The interband optical conductivity of Mo was calculated using a self-consistent relativistic band structure. Including electric dipole matrix elements, the results are in excellent quantitative agreement with experiment in the 1\char21{}6-eV region. The use of nonrelativistic bands and the neglect of the dipole matrix elements each lead to poorer agreement with experiment. The major relativistic effect is the lowering of the s-like bands, not the spin-orbit splitting. k-space searches identified the regions of the Brillouin zone contributing to the three principal structures, which were found to be large volumes of the zone consisting of general points, away from symmetry points or lines.