The need for replication of information storage , with system support for maintaining consistency among the various copies, has been widely recognized. However, earlier work guaranteed that copies would be consistent by assuring that connicting updates could not occur. Such an approach decreases availability for update, often at precisely the point when availability is desired. Further, there is increasing data that con-icting updates are extremely rare in many situations of interest. This paper presents a practical set of algorithms for maintaining the consistency of a replicated le system with an optimistic update policy. These algorithms permit a system which allows updates to an object so long as any copy is available; the algorithms then return the various copies to consistency at their rst opportunity. These algorithms have been used to build the Ficus replicated le system.