Rietica is a Rietveld structure refinement program currently running under Windows 95/98/NT. It is a Windows front end to the FORTRAN 77/90 program known as LHPM, which is available for a number of different computer operating systems.

Rietica helps create the text input file needed for LHPM as well as controls the refinement process. For beginners no knowledge of the input file is required (although knowledge of Rietveld analysis is required), but for advanced users an understanding of the input file allows quicker use of the program. A macro language based on BASIC allows scripting of complex refinements procedures, as well as intergration of other programs into Rietica.