IT’S official: The “Grey’s Anatomy” spin-off star ring LA-bound Addison is a “go” for next September.

The working title for the show is still “Private Practice,” but that could change, according to reports.

The new show, starring Kate Walsh, drew big ratings when it was previewed two weeks ago as part of a two-hour “Grey’s” episode.

Fan reaction was luke warm – most didn’t seem to like the lighter tone than “Grey’s.”

On the series, Addison, a neo-natal surgeon, leaves Seattle Grace hospital to set up a fertility clinic.