Initial project taken from: http://jira.codehaus.org/browse/JRUBY-191 To use this library (lib/win32ole.jar): brian@ORION$ jruby -J-Djava.library.path=lib -I lib -S examples\use_excel.rb The JACOB DLLs must be part of the 'java.library.path' and the jacob.jar must be on the JRuby classpath (using -I).