[en] After a general introduction the hydride and deuteride phases of Nb, Ta and V are discussed. Recent phase diagrams of the systems Nb-H(D), Ta-H(D), and V-H(D) are presented. The key diffusivities of H and D in the above metals are also covered. The basic thermodynamic relations required for an understanding of p-c-T data are given. Sieverts and various p-c-T curves pertaining to H and D in Nb, Ta and V are presented. Selected thermodynamic quantities and heats of phase transformations are included. Further topics include a discussion of localized vibrations, hydride morphologies, permeation, resistivity and property changes. (orig.)