Recently, three types of memories have been proposed as possible main memory extensions and replacements for head per track disks or drums; these are CCD, bubble, and BEAMOS memories.1,2,3The extent to which these memories come into widespread use will depend on such factors as cost, performance, reliability, maintainability and profitability. In this paper, potential areas of application for these memories are examined and some of the conditions which must be met for the memories to be economically attractive are determined for systems employing both a single job stream and multiprogrammed job streams.