Columns: District | Vacator | Reason for change | Successor | Date successor seated
Louisiana 1st | Richard A. Tonry (D) | Forced to resign May 4, 1977 | Bob Livingston (R) | August 27, 1977 | New York 21st | Robert García (R-L) | Changed parties February 21, 1978 | Robert García (D) | February 21, 1978 | Tennessee 5th | Clifford Allen (D) | Died June 18, 1978 | Vacant | Not filled this term | California 18th | William M. Ketchum (R) | Died June 24, 1978 | Vacant | Not filled this term | Illinois 1st | Ralph Metcalfe (D) | Died October 10, 1978 | Vacant | Not filled this term | Maryland 6th | Goodloe Byron (D) | Died October 11, 1978 | Vacant | Not filled this term | Wisconsin 6th | William A. Steiger (R) | Died December 4, 1978 | Vacant | Not filled this term | Wyoming At-large | Teno Roncalio (D) | Resigned December 30, 1978 | Vacant | Not filled this term | California 3rd | John E. Moss (D) | Resigned December 31, 1978 | Vacant | Not filled this term | California 14th | John J. McFall (D) | Resigned December 31, 1978 | Vacant | Not filled this term | California 33rd | Del M. Clawson (R) | Resigned December 31, 1978 | Vacant | Not filled this term | Kansas 5th | Joe Skubitz (R) | Resigned December 31, 1978 | Vacant | Not filled this term | Michigan 10th | Elford A. Cederberg (R) | Resigned December 31, 1978 | Vacant | Not filled this term | New Jersey 14th | Joseph A. LeFante (D) | Resigned December 31, 1978 | Vacant | Not filled this term | New York 9th | James Delaney (D) | Resigned December 31, 1978 | Vacant | Not filled this term | Texas 6th | Olin E. Teague (D) | Resigned December 31, 1978 | Vacant | Not filled this term | Texas 11th | William R. Poage (D) | Resigned December 31, 1978 | Vacant | Not filled this term