Every application which is Java-based (like IB TWS, for example) and some native OS X applications like Investor R/T. If you run Windows in a virtual machine, you can also run every Windows application you want. It's like running a Windows machine inside your mac: http://www.vmware.com/products/fusion/overview.html http://www.parallels.com/products/desktop/ Or, to put it short: Almost everything.