A user-oriented analysis is presented of file-related system call traces from a 4. 2 BSD UNIX system. The objective is twofold: (1) to establish a systematic approach to user-oriented analysis, and (2) to provide quantitative results useful for distributed file system design. A typical user as well as a typical file is characterized as a function of accesses made (which quantifies the notion of how heavily a file is used) and file size. Variations in the two characterizations about file categories (user-owned, notesfiles, etc. ) are quantified. The differences between the two characterizations are attributed to the nonuniformity among users since the differences almost disappear when users are categorized. The proposed method is shown to distinguish the nonuniform components of file access. Besides profiling a user's file usage, the results show that over 70% of users reference files owned by other users, that about 72% of permanent files are referenced in a read-only mode, and that the heavy users are characterized by large values of file I/O, accesses per file, file size, and number of files.