Win-SSI is a windows program to analyse soil structure interaction (SSI) problems using the CLASSI methodology. However, unlike many other SSI programs on the market Win-SSI offers a graphical user interface to guide you through the production of your SSI analyses, selecting from your personal library of soil profiles and time history sets. The GUI also checks that your output files form a valid QA set by carrying out checksum, date and time checks and produces plots to illustrate your work.