Right behind the shoulder and right at mid body, but that depends on the angle. I usually aim a touch higher than on a whitetail but that's mostly due to the hair factor that Shultzy mentioned and that I actually aim low on whitetails. (You don't have to worry about a bear ducking your arrow/jumping the string.)

http://www.wc.adfg.state.ak.us/index.cfm?adfg=huntalaska.shot