Data representation, data file specification, and the communication of data between software systems are playing increasingly important roles in clinical data management. This paper describes the concept of a self-documenting file that contains annotations or comments that aid visual inspection of the data file. We describe access of data from annotated files and illustrate data analysis with a few examples derived from the UNIX operating environment. Use of annotated files provides the investigator with both a useful representation of the primary data and a repository of comments that describe some of the context surrounding data capture.