Columns: State (class) | Vacator | Reason for change | Successor | Date of successors formal installation
Arkansas (2) | John L. McClellan (D) | Died November 28, 1977 | Kaneaster Hodges, Jr. (D) | December 10, 1977 | Montana (2) | Lee Metcalf (D) | Died January 12, 1978 | Paul G. Hatfield (D) | January 22, 1978 | Minnesota (1) | Hubert Humphrey (DFL) | Died January 13, 1978 | Muriel Humphrey (D) | January 25, 1978 | Alabama (3) | James Allen (D) | Died June 1, 1978 | Maryon Pittman Allen (D) | June 8, 1978 | Alabama (3) | Maryon Pittman Allen (D) | Successor elected November 7, 1978 | Donald Stewart (D) | November 7, 1978 | Minnesota (1) | Muriel Humphrey (DFL) | Successor elected November 7, 1978 | David Durenberger (R) | November 8, 1978 | Kansas (2) | James B. Pearson (R) | Resigned December 23, 1978 | Nancy Kassebaum (R) | December 23, 1978 | Mississippi (2) | James Eastland (D) | Resigned December 27, 1978 | Thad Cochran (R) | December 27, 1978 | Minnesota (2) | Wendell Anderson (DFL) | Resigned December 29, 1978 | Rudy Boschwitz (R) | December 30, 1978 | Wyoming (2) | Clifford Hansen (R) | Resigned December 31, 1978 | Alan K. Simpson (R) | January 1, 1979