IT'S MEREDITH AND DEREK'S WEDDING DAY, ON ABC'S "GREY'S ANATOMY"

"Grey's Anatomy" Celebrates its 100th Episode with an Event No Fan Should Miss

"What a Difference a Day Makes" � As Meredith, Derek and all of their friends prepare for the big wedding, a group of college students, injured in a car crash as they were heading to their graduation ceremony, is admitted to the ER. Meanwhile, Izzie fears the worst when she begins experiencing familiar symptoms, on "Grey's Anatomy," THURSDAY, MAY 7 (9:00-10:02 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, Katherine Heigl as Isobel "Izzie" Stevens, Justin Chambers as Alex Karev, T.R. Knight as George O'Malley, 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 and Kevin McKidd as Owen Hunt.

Guest cast tbd.

"What a Difference a Day Makes" 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 and Spanish audio via SAP. A TV parental guideline will be posted closer to airdate.

This episode of "Grey's Anatomy" will be available on ABC.com the day after airing on the network for users to watch online.