The Fifth International Workshop on Persistent Object Systems took place in the historic setting of Centro Studi "I Cappuccini" della Cassa di Risparmio di San Miniato. San Miniato (pisa). Italy from 1-4 September 1992. The workshop continued the tradition of the previous four in concentrating on the design. implementation and use of persistent systems. The other workshops in the series are: Venue Date Organisers Appin POSI 27-30 August Atkinson. Buneman 1985 Scotland and Morrison Appin POS2 25-28 August Atkinson and Morrison 1987 Scotland Newcastle POS3 10-13 January Koch and Rosenberg 1989 Australia POS4 23-27 September Marthas Vineyard DearIe. Mitchell 1990 USA andZdonik The series of Workshops on Database Programming Languages is closely related to the POS workshops. These have been held every other year out of phase with POS. and tend to concentrate on the design and theory of persistent systems. The workshops in the DBPL series are: Date Venue Organisers DBPL 1 7-10 September Roscoff Bancilhon and France 1987 Buneman DBPL2 4-8 June Salishan Hull. Morrison and 1989 USA Stemple 27-30 August Nafplion Kanellakis and DBPL3 Greece Schmidt 1991 Preface vi This book follows the format of the workshop. Of the 39 papers submitted for the workshop, 22 were accepted in order to allow plenty of time for discussion. As at POS 4 in Marthas Vineyard each paper was followed by 5 minutes of questions and each session by a 30 minute discussion.