All states recognize DOs and have for some time now.
Until recently (within the last year or so) Lousiana wouldn't recognize the COMLEX, so you'd have to take USMLE to practice there. Now they'll accept the COMLEX, so it's accepted by every state.
There are five states that require DOs to do the AOA internship (OK, MI, FL, PA, and WV) in order to become licensed, however, you can get an ACGME transitional year "approved" somehow (I don't know the details of this, and there's a discussion on the Rotations board about it if you're interested). I've also heard that MI and PA are more strict, and the others are more lenient about approval of ACGME stuff, but that's hearsay, so I wouldn't really go by that.
