1) Go to www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX The program archives are named Perple_X_#.#.#_***.zip where #.#.# is the version number (e.g., 6.8.6) and *** indicates compiler, system and/or author information. The OSX versions are provided courtesy of third parties. As of Feb 22, 2019 the two third party authors/versions are both compiled with gfortran: JS - John Schumacher, Bristol - is dynamically linked. MC - Mark Caddick, Virginia Tech - is statically linked. The compiler options used to generate these versions can have major performance consequences. Perhaps more importantly, dynamically linked versions will (usually) require that you install the gcc libraries. To install these libraries refer to https://groups.io/g/PerpleX/message/1658 The OSX versions may not be current. Check the update file: www.perplex.ethz.ch/perplex_updates.html to establish whether the archive contains programs with bugs that may have consequences for you. Choose and extract the programs from the archive of your choice to a single directory. If you wish to compile your own version of Perple_X, contact me and I will provide you with the current link for the FORTRAN sources. 2) Extract the Perple_X data files in: www.perplex.ethz.ch/perplex/ibm_and_mac_archives/Perple_X_#.#.#_data_files.zip to the same directory as in step 1. Select the version #.#.# closest to the program version #.#.# in step 1, but do not use data files with a higher version number than the program version number. 3) Run Perple_X programs from a shell (aka terminal window). Configure the shell so that the directory in step 1 is the default current working directory. Running Perple_X by clicking on the program icons can cause confusion, but, if you insist, then refer to the instructions at: www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX/DoubleClickPerplex.pdf additional useful Apps are at: www.perplex.ethz.ch/perplex/ibm_and_mac_archives/OSX/Perple_X_OSX_Apps.zip 4) Follow the remaining instructions at www.perplex.ethz.ch/perplex/ibm_and_mac_archives/README_COMMON_INSTRUCTIONS.txt