This is a shareware guide to the usage of the public-domain groundwater flow program MODFLOW. Most versions of MODFLOW are for DOS or UNIX but there are also MacIntosh and Windows compatible versions. The guide does not include MODFLOW itself but does tell how to get both free and commercial versions of the program. Versions of the guide are available for Windows, Mac, and Unix. Installation: Extract all the files to the same directory Using help file: Open mfhelp.htm as a local file with any web browser. So far, it has only been tested on NSCA MOSAIC 2.0 and NETSCAPE 1.22. Distributions status: This guide may be freely distributed. There is a $25 registration fee. Author's address: Richard B. Winston Department of Geology and Geophysics Lousiana State University Baton Rouge, La 70806 USA tel. 504-388-2337 fax. 504-388-2302 email: rwinsto@lsuvm.sncc.lsu.edu