Open the Preference window using the Preferences menu item on the File menu.
There is a Fonts item in the Preferences that will let you customize the
fonts used in each of the Desktop tools. If you're using the latest version
of MATLAB, this page from the online documentation contains images showing
exactly where those preferences are located.
http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_env/f1-70353.html
If you're using an older version, try searching for "font preferences" in
the Help Browser to bring up the corresponding page with screen shots from
your version.
--
Steve Lord
sl...@mathworks.com