Deuteron magnetic resonance has been used to measure line shapes and relaxation rates in a series of Ta, Nb, and V deuterides between 190 and 580 K. Results are compared with corresponding data in hydrides to reveal dipolar, quadrupolar, and electronic rate contributions in various phases. Korringa constants, diffusion activation energies, and the effects of magnetic and electric field inhomogeneities are examined. Deuteron relaxation associated with hopping among tetrahedral interstitial sites in ..cap alpha.. phases is primarily quadrupolar. In the warm portions of the ..beta.. phase, the dominant relaxation is dipolar because the deuteron hopping occurs only among an ordered subset of interstitial sites. At lower temperatures quadrupolar relaxation again dominates, before decreasing around 200 K.