The 108th United States Congress began on January 3, 2003. There were nine new senators (seven Republicans, two Democrats) and 53 new representatives (32 Republicans, 21 Democrats), as well as one new delegate (a Democrat), at the start of its first session. Additionally, four representatives (three Democrats, one Republican) took office on various dates in order to fill vacancies during the 108th Congress before it ended on January 3, 2005.
Due to redistricting after the 2000 census, 16 representatives were elected from newly established congressional districts.
| District | Delegate | Switched party | Prior background | Birth year |
|---|---|---|---|---|
| Guam at-large | Madeleine Bordallo (D) | No | Lieutenant Governor of Guam | 1933 |
| District | Representative | Took office | Switched party | Prior background | Birth year |
|---|---|---|---|---|---|
| Texas 19 | Randy Neugebauer (R) | June 5, 2003 | No | City councilor | 1949 |
| Kentucky 6 | Ben Chandler (D) | February 17, 2004 | Yes | Attorney General of Kentucky | 1959 |
| South Dakota at-large | Stephanie Herseth (D) | June 1, 2004 | Yes | Law clerk | 1970 |
| North Carolina 1 | G. K. Butterfield (D) | July 20, 2004 | No | North Carolina Supreme Court | 1947 |
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