| "Tainted Obligation" | |
|---|---|
| Grey's Anatomy episode | |
 Alex Karev (Justin Chambers) screaming after his confrontation with a bear. | |
| Episode no. | Season 6 Episode 4 |
| Directed by | Tom Verica |
| Written by | Jenna Bans |
| Featured music | "Trading Things In" "Come On Be Good" "Long Time Gone" "Wish You Well" "Morning Mist" |
| Original air date | October 8, 2009 |
| Running time | 43 minutes |
| Guest appearances | |
| |
"Tainted Obligation" is the fourth episode of the sixth season of the American television medical drama Grey's Anatomy, and the 106th episode overall. Written by Jenna Bans and directed by Tom Verica, the episode aired on the American Broadcasting Company (ABC) in the United States on October 8, 2009.
The episode focuses on Meredith Grey (Ellen Pompeo) and Lexie Grey (Chyler Leigh) as their father, Thatcher Grey (Jeff Perry), is admitted to the hospital in need of a liver transplant. Meanwhile, Cristina Yang (Sandra Oh) worries about losing her job, and Owen Hunt (Kevin McKidd) works with Izzie Stevens (Katherine Heigl) on a challenging surgery for a terminal patient.
Although the episode was fictionally set in Seattle, Washington, filming primarily took place in Los Angeles, California. Perry reprised his role as a guest star, while Ralph Waite and Jocko Sims made their first appearances. The title of the episode refers to the song "Tainted Obligation" by the American alternative rock group Community Trolls.
Upon its initial airing, "Tainted Obligation" was viewed by 14.13 million Americans, and garnered a 5.4/14 Nielsen rating/share in the 18–49 demographic, ranking #3 for the night in terms of viewership. It received positive reviews from television critics, with high praise for the performances of Pompeo and Leigh.