Columns: District | Incumbent | Party | First elected | Result | Candidates
Illinois 3 | Fred E. Busbey | Republican | 1946 | Lost re-election Democratic gain | Neil J. Linehan (D) 52.9% Fred E. Busbey (R) 47.1% | Illinois 5 | Martin Gorski Redistricted from 4th | Democratic | 1942 | Re-elected | Martin Gorski (D) 72.4% John L. Waner (R) 27.6% | Illinois 14 | Chauncey W. Reed Redistricted from 11th | Republican | 1934 | Re-elected | Chauncey W. Reed (R) 68.3% Richard Plum (D) 31.7% | Illinois 15 | Noah M. Mason Redistricted from 12th | Republican | 1936 | Re-elected | Noah M. Mason (R) 56.4% G. M. Wells (D) 43.6% | Illinois 17 | Leslie C. Arends | Republican | 1934 | Re-elected | Leslie C. Arends (R) 62.8% Carl Vrooman (D) 37.2% | Illinois 18 | Everett Dirksen Redistricted from 16th | Republican | 1932 | Retired Republican hold | Harold H. Velde (R) 52.1% Dale E. Sutton (D) 47.9% | Illinois 20 | Sid Simpson | Republican | 1942 | Re-elected | Sid Simpson (R) 53.1% Henry D. Sullivan (D) 46.9% | Illinois 20 | Anton J. Johnson Redistricted from 14th | Republican | 1938 | Retired Republican loss | Sid Simpson (R) 53.1% Henry D. Sullivan (D) 46.9% | Illinois 26 | C. W. Bishop | Republican | 1940 | Re-elected | C. W. Bishop (R) 51.9% Kent E. Keller (D) 48.1%