Optical storage of information offers the potential advantages of high packing density, fast access and low cost. Present research and development on optical memories is divided into two main approaches: those employing bit by bit direct imaging and those employing page organized holograph coding. Each of these categories can be further subdivided on the basis of whether the storage medium is reversible or irreversible. In this paper we will review all four types with emphasis given to the present state of the art and possible future developments. A further class of optical systems which involve the storage of information in non-digital form, i.e. as either direct or holographic images of pictures or documents, is beyond the scope of the present discussion.