The Republicans held three seats in primary contests:
 Delaware: T. Coleman du Pont (R) defeated L. Heisler Ball (R) in the primary and then won the general. Illinois: Charles S. Deneen (R) defeated Medill McCormick (R) in the primary and then won the general. South Dakota: William H. McMaster (R) defeated Thomas Sterling (R) in the primary and then won the general. The Democrats held two seats in primary contests:
 South Carolina: Coleman L. Blease (D) defeated Nathaniel B. Dial (D) in the primary and was unopposed in the general. Tennessee: Lawrence D. Tyson (D) defeated John K. Shields (D) in the primary and was unopposed in the general. Change in Senate composition

Before the elections 
At the beginning of 1924. After the general elections

After the special elections

Race summaries

Special elections during the 68th Congress 
In these special elections, the winners were seated during 1924 or before March 4, 1925; ordered by election date. Elections leading to the 69th Congress 
In these general elections, the winners were elected for the term beginning March 4, 1925; ordered by state. All of the elections involved the Class 2 seats.
The Republicans held three seats in primary contests:
Delaware: T. Coleman du Pont (R) defeated L. Heisler Ball (R) in the primary and then won the general. 
Illinois: Charles S. Deneen (R) defeated Medill McCormick (R) in the primary and then won the general.
South Dakota: William H. McMaster (R) defeated Thomas Sterling (R) in the primary and then won the general.

The Democrats held two seats in primary contests:
South Carolina: Coleman L. Blease (D) defeated Nathaniel B. Dial (D) in the primary and was unopposed in the general.
Tennessee: Lawrence D. Tyson (D) defeated John K. Shields (D) in the primary and was unopposed in the general. Change in Senate composition

Before the elections
At the beginning of 1924. After the general elections

After the special elections

Race summaries

Special elections during the 68th Congress
In these special elections, the winners were seated during 1924 or before March 4, 1925; ordered by election date. Elections leading to the 69th Congress
In these general elections, the winners were elected for the term beginning March 4, 1925; ordered by state. All of the elections involved the Class 2 seats.