Volume phase holograms are holograms stored throughout a material whose thickness is much greater than the wavelength of light. This paper is a review of the present state of the art in volume holographic storage in ferroelectric crystals. We shall be concerned principally with Fe-doped LiNbO3 since it is the most extensively studied member of this class of materials and to date exhibits the best performance characteristics of any member of this class of materials. Results obtained for other dopants or host materials will be discussed only where important, both because less is known about them and because they are either not as sensitive or do not possess the fixing capability of Fe-doped LiNb0 3. Systems based on this storage technique can be configured either for write/read applications where high recording sensitivity and fast erasure are required or for archival storage where a fixing capability is required.