This chapter describes how to install X-PLOR and how to change the array dimensions of the program. X-PLOR has been tested extensively on VAX/VMS, CRAY-YMP, CONVEX C220, STELLAR GS2000, SGI 4D/220, and NeXT. These machines are referred to as ``supported." A large number of ``unsupported" installation procedures are supplied on the X-PLOR distribution tape as well, in particular for FPS 511EA Series, IBM 3090 (CMS), ALLIANT, CYBER205, IBM6000, ESV, SUN, and HP720. These installation procedures are presented here courtesy of various X-PLOR users. They have not been tested with the current version and may require modification. The supported installation procedures should provide sufficient information if the user runs into problems.