Because of the growing number of digital data sources-from satellites such as the LANDSAT series to the increasing use of all-digital information distribution networks in the publishing industries-there has been a corresponding explosion in the need to store that data permanently at very high densities such that it can be retrieved conveniently and quickly. In parallel with these developments, the capability of high density optical data storage and retrieval techniques such as holography and optical spot recording to meet these needs has improved as well. Offering data transfer rates of up to 100 Mb/sec (spot recording) to over 1 Gb/sec (holographic) and information storage densities in excess of 100 Mb/in2, these technologies have now made it possible to configure complete systems for a wide range of mass storage requirements. The basic technologies and building blocks required for such systems, the general criteria for converting a mass memory specification to an optical storage system based on it, and examples of both holographic and direct spot systems are described. The present status of the Wideband Holographic Recorder System, with data transfer rates of over 1 Gb/sec, and the MASTAR 1015 bit archival mass memory with information storage densities of over 100 Mb/in2, are also reviewed.