This book constitutes the refereed proceedings of the 5th International Service Availability Symposium, ISAS 2008, held in Tokyo, Japan, in May 2008.

The 12 revised full papers presented together with 2 keynote papers and 2 tutorials were carefully reviewed and selected from 28 submissions. The papers are organized in topical sections on enterprise system dependability, software service availability, service availability platform, and service dependability analysis.