Conversion, the word is enough to dim the enthusiasm of most systems developers. The word instills fear in some, trepidation and loathing in others. This chapter deals with the various forms of the conversion of data. Conversion efforts can be as challenging as any state-of-the-art technology. They can exercise the most creative abilities of technology professionals. There are a number of different ways to classify a data conversion. One of the most common ways is to classify it by what is involved in the conversion effort. In general, the simplest conversion is upgrading hardware, assuming that all of the other variables remain constant, i.e., operating systems, file access method, coding structure and format, and application software. Changes to the operating system are generally more complicated from a conversion perspective, than changes to hardware. The complexity is usually more pronounced at the application software rather than the data level.