Kate Walsh (Addison Montgomery) will be starring in a spin-off, "Private Practice", but will still do guest appearances and did several cross-overs between the two shows until Private Practice was cancelled in 2013Isaiah Washington (Preston Burke) was fired from the show, therefore will not be returning after Season 3. But made a guest appearance in season 10.Brooke Smith (Erica Hahn) has chosen not to renew her contract, because she felt the writers weren't really doing anything with her character.T.R. Knight (George O'Malley) asked to be released from his contract at the end of Season 5 so he can pursue other projects.As of the beginning of Season 6, Katherine Heigl (Izzie Stevens) has stepped back as a regular and is now recurring, due to pursuing other projects and adopting a daughter.Both Nora Zehetner (Reed Adamson) and Robert Baker (Charles Percy) did not return for Season 7, as both their characters were shot dead in the Season 6 finale.
Lexie Grey (Chyler Leigh) left the show to spend more time with her family and her character died Season 8, episode 24. Her love interest on the show
Mark Sloan (Eric Dane) made his last appearance Season 9, episode 2 after reported budget cuts to the show.Kim Raver (Dr. Teddy Altman) left in 2012 also due to budget cuts.Sandra Oh(Cristina Yang) left the series as a main character in the Season 10 finale after deciding to spend more time persuing other career avenues. Along with her went Gaius Charles ... (Dr. Shane Ross)