(Somewhat ESMF specific) The following is a magic file: /usr/local/matlab/toolbox/local/startup.m You create it by copying /usr/local/matlab/toolbox/local/startupsav.m You can then put in "addpath directory" commands, to add things to your toolbox. The toolbox additions can be directories under /usr/local/matlab/toolbox Matlab binaries on AIX appear to be 32 bit only, so if you have libraries you need to link matlab stuff with, you'll need 32 bit versions of those libraries (EG libnetcdf). http://www.mathworks.com/support/sysreq/index.html?parenttopic=System%20Compatibility