| Hugh Laurie | Dr. Gregory House |
| Lisa Edelstein | Dr. Lisa Cuddy |
| Omar Epps | Dr. Eric Foreman |
| Robert Sean Leonard | Dr. James Wilson |
| Jennifer Morrison | Dr. Allison Cameron |
| Jesse Spencer | Dr. Robert Chase |
| Peter Jacobson | Dr. Chris Taub |
| Olivia Wilde | Thirteen |
| David Strathairn | Nash |
| Neill Barry | Donald |
| Riki Lindhome | Sarah |
| Vernee Watson | Nurse Smits
(as Vernée Watson) |
| Shelly Cole | Nurse Maldonado |
| Riley Thomas Stewart | Walker |
| Dava Krause | Daria |
| Al Foster | Davies |
| Tom Billett | Security Guard #1 |
| Bobbin Bergstrom | Nurse |
| Tamara Kelly | Woman Patient
(scenes deleted) |
| David Zahedian | Woman Patient's Husband
(scenes deleted) |
| Reid Gormly | Doctor #2
(uncredited) |