| Alabama | Richard Shelby | Republican | Re-elected, 68% | Wayne Sowell (Democrat) 32% |
| Alaska | Lisa Murkowski | Republican | Elected, 48.6% | Tony Knowles (Democrat) 45.5% Marc Millican (Independent) 2.9% Jerry Sanders (Alaskan Independence) 1.2% Jim Sykes (Green) 1% Scott Kohlhaas (Libertarian Party) 0.4% |
| Arizona | John McCain | Republican | Re-elected, 76% | Stuart Starky (Democrat) 21% Ernest Hancock (Libertarian) 3% |
| Arkansas | Blanche Lincoln | Democratic | Re-elected, 56% | Jim Holt (Republican) 44% |
| California | Barbara Boxer | Democratic | Re-elected, 57.7% | Bill Jones (Republican) 37.8% Marsha Feinland (Peace and Freedom) 2% James P. Gray (Libertarian) 1.8% Don J. Grundmann (Constitution) 0.7% |
| Colorado | Ben Nighthorse Campbell | Republican | Retired: Democratic victory | Ken Salazar (Democrat) 51.3% Pete Coors (Republican) 46.5% Doug Cambell (Constitution) 1% Richard Randall (Libertarian) 0.5% John Harris (Independent) 0.4% Victor Good (Reform Party) 0.3% |
| Connecticut | Christopher Dodd | Democratic | Re-elected, 66% | Jack Orchulli (Republican) 32% Timothy Knibbs (C) 1% Lenny Rasch (L) 1% |
| Florida | Bob Graham | Democratic | Retired: Republican victory | Mel Martinez (Republican) 49% Betty Castor (Democratic) 48% Dennis Bradley (Veterans) 2% |
| Georgia | Zell Miller | Democratic | Retired: Republican victory | Johnny Isakson (Republican) 58% Denise Majette (Democrat) 40% Allen Buckley (Libertarian) 2% |
| Hawaii | Daniel Inouye | Democratic | Re-elected, 76% | Campbell Cavasso (Republican) 21% James Brewer (Independent) 2% Lloyd Mallan (Libertarian) 1% |
| Idaho | Mike Crapo | Republican | Re-elected, 99% | Write-in for Scott McClure (Democrat) 1% |
| Illinois | Peter Fitzgerald | Republican | Retired: Democratic victory | Barack Obama (Democrat) 70% Alan Keyes (Republican) 27% Albert Franzen (Independent) 2% Jerry Kohn (Libertarian) 1% |
| Indiana | Evan Bayh | Democratic | Re-elected, 62% | Marvin Scott (Republican) 37% Albert Barger (Libertarian) 1% |
| Iowa | Chuck Grassley | Republican | Re-elected, 70.1% | Arthur Small (Democrat) 27.9% Christy Welty (Libertarian) 1% Daryl Northrop (Green) 0.8% Edwin Fruit (Socialist Workers) 0.1% |
| Kansas | Sam Brownback | Republican | Re-elected, 69% | Lee Jones (Democrat) 28% Stephen A. Rosile (Libertarian) 2% George Cook (Reform) 1% |
| Kentucky | Jim Bunning | Republican | Re-elected, 51% | Daniel Mongiardo (Democrat) 49% |
| Louisiana | John Breaux | Democratic | Retired: Republican victory | David Vitter (Republican) 51% Chris John (Democrat) 29% John N. Kennedy (Democrat) 15% Arthur Morrell (Democrat) 3% Richard Fontanesi (Independent) 1% R.A. Galan (Independent) 1% Sam Melton (Democrat) 1% |
| Maryland | Barbara Mikulski | Democratic | Re-elected, 64.8% | E. J. Pipkin (Republican) 33.7% Maria Allwine (Green) 1.1% Thomas Trump (Constitution) 0.4% |
| Missouri | Kit Bond | Republican | Re-elected, 56% | Nancy Farmer (Democrat) 42.8% Kevin Tull (Libertarian) 0.7% Don Griffin (Constitution) 0.4% |
| Nevada | Harry Reid | Democratic | Re-elected, 61.1% | Richard Ziser (Republican) 35.1% None of These Candidates 1.6% Tomas Hurst (Libertarian) 1.2% David Schumann (Constitution) 0.7% Gary Marinch (Natural Law) 0.3% |
| New Hampshire | Judd Gregg | Republican | Re-elected, 66% | Doris Haddock (Democrat) 34% |
| New York | Chuck Schumer | Democratic | Re-elected, 71.16% | Howard Mills (Republican) 24.24% Marilyn O'Grady (Conservative) 3% David McReynolds (Green) 0.5% Donald Silberger (Libertarian) 0.3% Abe Hirschfeld (Builders Party) 0.2% Martin Koppel (Socialist Workers) 0.2% |
| North Carolina | John Edwards | Democratic | Retired: Republican victory | Richard Burr (Republican) 52% Erskine Bowles (Democrat) 47% Tom Bailey (Libertarian) 1% |
| North Dakota | Byron Dorgan | Democratic-NPL | Re-elected, 68% | Mike Liffrig (Republican) 32% |
| Ohio | George Voinovich | Republican | Re-elected, 64% | Eric Fingerhut (Democrat) 36% |
| Oklahoma | Don Nickles | Republican | Retired: Republican victory | Tom Coburn (Republican) 53% Brad Carson (Democrat) 41% Sheila Bilyeu (Independent) 6% |
| Oregon | Ron Wyden | Democratic-Oregon | Re-elected, 63% | Al King (Republican) 32% Teresa Keane (Pacific Green) 2% Dan Fitzgerald (Libertarian-Oregon) 2% David Brownlow (Constitution-Oregon) 1% |
| Pennsylvania | Arlen Specter | Republican | Re-elected, 53% | Joe Hoeffel (Democrat) 42% Jim Clymer (Constitution) 4% Betsy Summers (Libertarian) 1% |
| South Carolina | Ernest "Fritz" Hollings | Democratic | Retired: Republican victory | Jim DeMint (Republican) 53.7% Inez Tenenbaum (Democrat) 44.1% Patrick Tyndall (Constitution) 0.8% Rebekah Sutherland (Libertarian) 0.7% Tee Ferguson (United Citizens Party) 0.4% Efia Nwangaza (Green) 0.3% |
| South Dakota | Tom Daschle | Democratic | Defeated, 49% | John Thune (Republican) 51% |
| Utah | Robert Foster Bennett | Republican | Re-elected, 69% | Paul Van Dam (Democrat) 28% Gary R. Van Horn (Constitution) 2% Joe Labonte (Personal Choice) 1% |
| Vermont | Patrick Leahy | Democratic | Re-elected, 70.6% | Jack McMullen (Republican) 24.5% Cris Ericson (Marijuana) 2.1% Craig Hill (Green) 1.3% Keith Stern (Independent) 1.1% Ben Mitchell (Liberty Union) 0.3% |
| Washington | Patty Murray | Democratic | Re-elected, 55% | George Nethercutt (Republican) 43% J. Mills (Libertarian) 1% Mark Wilson (Green) 1% |
| Wisconsin | Russ Feingold | Democratic | Re-elected, 55.4% | Tim Michels (Republican) 44.1% Arif Khan (Libertarian) 0.3% Eugene Hem (Independent) 0.2% |