Democrats won open seats in Colorado, South Dakota, and New York while ousting incumbents in Georgia and Illinois.

Republicans won an open seat in Kentucky while ousting an incumbent in Indiana.

They gained five seats in Texas after a controversial mid-decade redistricting placed several rural Democratic incumbents into new districts.

Two seats opened early due to resignations and were not filled until the November elections.

On December 4, 2004, a run-off election was held to determine the winner of the 3rd and 7th congressional districts.

In the 3rd district, Charlie Melancon narrowly defeated Billy Tauzin III.

All seven incumbents who ran for re-election, none of whom faced viable challengers, were returned to Congress.