IN A SHOCKING TWO-HOUR SEASON FINALE, A CRISIS UNLIKE ANY BEFORE UNFOLDS AT SEATTLE GRACE, AND MEREDITH AND CRISTINA'S SURGICAL SKILLS ARE PUT TO THE ULTIMATE TEST, ON ABC'S "GREY'S ANATOMY"

Mandy Moore ("A Walk To Remember") Guest Stars

"Sanctuary" - In the first hour of the two-hour season six finale, Seattle Grace Hospital is hit with a crisis like no other in its' history, on "Grey's Anatomy," THURSDAY, MAY 20 (9:00-10:00 p.m., ET) on the ABC Television Network.

In the second hour of the season finale, "Death and All His Friends," Cristina and Meredith's surgical skills are put to the ultimate test, on "Grey's Anatomy," THURSDAY, MAY 20 (10:00-11:00 p.m., ET) on the ABC Television Network.

"Grey's Anatomy" stars Ellen Pompeo as Meredith Grey, Patrick Dempsey as Derek Shepherd, Sandra Oh as Cristina Yang, Justin Chambers as Alex Karev, Chandra Wilson as Miranda Bailey, James Pickens, Jr. as Richard Webber, Sara Ramirez as Callie Torres, Eric Dane as Mark Sloan, Chyler Leigh as Lexie Grey, Kevin McKidd as Owen Hunt and Jessica Capshaw as Arizona Robbins.

Guest starring Mandy Moore as Mary and Ryan Devlin as Bill. Other guest cast tba.

"Sanctuary" was written by Shonda Rhimes and directed by Stephen Cragg. "Death And All His Friends" was written by Shonda Rhimes and directed by Rob Corn.

"Grey's Anatomy" is broadcast in 720 Progressive (720P), ABC's selected HDTV format, with 5.1-channel surround sound. A TV parental guideline will be assigned closer to airdate.

For more information on "Grey's Anatomy," visit ABC.com.