Senators representing even-numbered districts were newly elected for this session and were serving the first two years of a four-year term.

Senators representing odd-numbered districts were serving the third and fourth year of a four-year term, having been elected in the general election of November 5, 1974.

[1] The governor of Wisconsin for the first six months of this term was Democrat Patrick Lucey, of Crawford County, serving the third year of his second four-year term, having won re-election in the 1974 Wisconsin gubernatorial election.

Lucey resigned on July 6, 1977, to accept appointment as United States Ambassador to Mexico.

At that time, the lieutenant governor, Democrat Martin J. Schreiber, of Milwaukee County, then ascended to become governor for the remainder of this legislative term.