According to the manual page that ships with OS X:
… it looks for
~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The
--noprofileoption may be used when the shell is started to inhibit this behavior.
.profile works with
.bash_profile is bash-specific and will override
.profile if present.
mac OS X environment checks
.profile in this order. It will run whichever is the highest in the hierarchy, so, if you have
.bash_profile, it will not check