Persistent object systems are systems which support the creation and manipulation of objects in a uniform manner, regardless of how long they persist. This is in direct contrast to conventional systems where temporary objects are created and manipulated using one mechanism (typically programming language data structures), and permanent objects are maintained using a different mechanism (usually a file name). This volume contains 22 papers presented at the Fifth International Workshop on Persistent Object Systems, which was held in San Miniato (Pisa), Italy, from 1-4 September 1992. As with previous workshops, the main topics for discussion were the design, implementation and use of persistent object systems. The workshop aimed to encourage the exchange of ideas among members of the international research community who are actively engaged in this area. "Persistent Object Systems" provides a snapshot of state-of-the-art research into this important area. It will provide useful reading for researchers and postgraduate students in software engineering and programming languages.