In every election cycle a certain number of representatives retire leaving behind open seats for their parties to defend. In 2018, the number of open seats, especially Republican held seats, is unusually large. Here are the number of retirements in recent years:
| Year | Democrats | Republicans |
| 2016 | 18 | 25 |
| 2014 | 17 | 25 |
| 2012 | 22 | 19 |
| 2010 | 17 | 20 |
| 2008 | 6 | 27 |
| 2006 | 9 | 18 |
This year 19 Democrats and 38 Republicans are retiring at the end of their current term.
Here are the announced retirements so far, sorted on PVI (Partisan Voting Index).
Any seat between R+5 and D+5 is a swing district that has to be fought over, even more so
if occupied by the other party.
Pennsylvania districts are not included since the courts redrew the entire map this year.
| Representative | Party | District | PVI | Reason for leaving |
| Diane Black | Republican | TN-06 | R+24 | Ran for governor and lost primary |
| Marsha Blackburn | Republican | TN-07 | R+20 | Running for senator |
| Evan Jenkins | Republican | WV-03 | R+23 | Running for senator |
| Raul Labrador | Republican | ID-01 | R+21 | Running for governor |
| Diane Black | Republican | TN-06 | R+20 | Running for governor |
| John Duncan Jr. | Republican | TN-02 | R+20 | Retiring from public office |
| Luke Messer | Republican | IN-06 | R+18 | Running for senator |
| Todd Rokita | Republican | IN-04 | R+17 | Running for senator |
| Jim Bridenstine | Republican | OK-01 | R+17 | Was appointed NASA administrator |
| Kevin Cramer | Republican | ND-AL | R+16 | Running for senator |
| Jeb Hensarling | Republican | TX-05 | R+16 | Retiring from public office |
| Harold "Trey" Gowdy III | Republican | SC-04 | R+5 | Retiring from public office |
| Kristi Noem | Republican | SD-AL | R+14 | Running for governor |
| Bob Goodlatte | Republican | VA-06 | R+13 | Retiring from public office |
| Gregg Harper | Republican | MS-03 | R+13 | Retiring from public office |
| Sam Johnson | Republican | TX-03 | R+13 | Retiring from public office |
| Tom Rooney | Republican | FL-17 | R+13 | Retiring from public office |
| Ted Poe | Republican | TX-02 | R+11 | Retiring from public office |
| Chris Collins | Republican | NY-27 | R+11 | Arrested for insider trading |
| Lynn Jenkins | Republican | KS-02 | R+10 | Retiring from public office |
| Lamar Smith | Republican | TX-21 | R+10 | Retiring from public office |
| Mark Sanford | Republican | SC-01 | R+10 | Lost renomination |
| Joe Barton | Republican | TX-06 | R+9 | Got caught sending out dirty pictures |
| James Renacci | Republican | OH-16 | R+8 | Running for governor |
| Robert Pittenger | Republican | NC-09 | R+7 | Lost renomination |
| Ron DeSantis | Republican | FL-06 | R+7 | Running for governor |
| Steve Pearce | Republican | NM-02 | R+6 | Running for governor |
| Dennis Ross | Republican | FL-15 | R+6 | Retiring from public office |
| Tom Garrett | Republican | VA-05 | R+6 | White nationalism, alcohol problem |
| Paul Ryan | Republican | WI-01 | R+5 | Couldn't take the heat any more |
| Tim Walz | Democratic | MN-01 | R+5 | Running for governor |
| Dave Trott | Republican | MI-11 | R+4 | Retiring from public office |
| Rick Nolan | Democratic | MN-08 | R+4 | Retiring from public office |
| Rodney Frelinghuysen | Republican | NJ-11 | R+3 | Retiring from public office |
| Carol Shea-Porter | Democratic | NH-01 | R+2 | Retiring from public office |
| Jacky Rosen | Democratic | NV-03 | R+2 | Running for senator |
| Darrell Issa | Republican | CA-49 | R+1 | Retiring from public office |
| Frank LoBiondo | Republican | NJ-02 | R+1 | Retiring from public office |
| Martha McSally | Republican | AZ-02 | R+1 | Running for senator |
| Dave Reichert | Republican | WA-08 | Even | Retiring from public office |
| Ed Royce | Republican | CA-39 | Even | Retiring from public office |
| Elizabeth Esty | Democratic | CT-05 | D+2 | She failed to fire abusive staffer |
| Ruben Kihuen | Democratic | NV-04 | D+3 | Sex scandal |
| Sander Levin | Democratic | MI-09 | D+4 | Has a position at the University of Michigan |
| Kyrsten Sinema | Democratic | AZ-09 | D+4 | Running for senator |
| Ileana Ros-Lehtinen | Republican | FL-27 | D+5 | Retiring from public office |
| John Delaney | Democratic | MD-06 | D+6 | Running for president |
| Michelle Lujan-Grisham | Democratic | NM-01 | D+7 | Running for governor |
| Louise Slaughter | Democratic | NY-25 | D+8 | Louise Slaughter died |
| Niki Tsongas | Democratic | MA-03 | D+9 | Retiring from public office |
| Jared Polis | Democratic | CO-02 | D+9 | Running for governor |
| Colleen Hanabusa | Democratic | HI-01 | D+17 | Running for governor |
| Beto O'Rourke | Democratic | TX-16 | D+17 | Running for senator |
| Gene Green | Democratic | TX-29 | D+19 | Retiring from public office |
| Keith Ellison | Democratic | MN-05 | D+26 | Running for attorney general |
| John Conyers | Democratic | MI-13 | D+32 | Sex scandal |
| Luis Gutierrez | Democratic | IL-04 | D+33 | Retiring from public office |
In addition, there are seven vacancies in the House. All require special elections. However, some of these will be held on election day (MI-13, PA-07, and PA-15), which is effectively the same as an open seat, since no incumbent will be running. For this reason, we have counted these as retirements, rather than resignations.
Furthermore, special elections will be held in OH-12 on Aug. 7, TX-27 on June 30, and in OK-01 and NY-25 on dates to be determined.