X-Ray diffraction techniques were used to establish a partial constitutional diagram for the vanadium-hydrogen system. At room temperature the primary solid solution (b.c.c.) extends to VHo.os. A body-centered tetragonal hydride phase was found between compositions VHo.4sa nd VHo.gow ith axial ratio (c/a) increasing from 1.100 to 1.126. A twophase field exists at intermediate compositions. A second two-phase region extends from VHo.go to the maximum hydrogen content studied, ie., VHI.80. Additional studies at higher temperatures (up to 320’) show the variation in lattice parameters with temperature and hydrogen content.