μPDSM, a powder diffraction search/match system, is derived from the original interactive time-sharing system written for the NIH/EPA Chemical Information System. Transformed and essentially rewritten, it still searches the entire JCPDS database, but on an inexpensive IBM PC microcomputer. In the transition from mainframe to micro, μPDSM has lost none of its speed or performance. Indeed, the basic discriminating power of the search/match algorithms had to be improved, since the Powder Diffraction File is some 50% larger than it was when The CIS version was in operation. While μPDSM will solve typical problems on a “push-button” mode, it provides an environment that promotes optimization of search parameters by the diffractionist, and provides all of the subfile and chemistry functions associated with larger systems.