In 1918 the constituency consisted of "The county of Bute, inclusive of all burghs, situated therein, and the county district of Northern Ayr, inclusive of all burghs situated therein except insofar as included in the Ayr District of Burghs".
In 1950 some of the constituency was transferred to the then new constituency of Central Ayrshire.
1918–1950: The county of Bute, and the county district of Northern Ayr, inclusive of all burghs therein except in so far as included in the Ayr District of Burghs.[2]
1950–1955: The county of Bute, the burghs of Ardrossan, Largs, and Saltcoats, and the district of Saltcoats.[3]
1955–1983: The county of Bute, the burghs of Ardrossan, Largs, Saltcoats, and Stevenston, and the district of Saltcoats.[4]
General Election 1939–40:
Another General Election was required to take place before the end of 1940. The political parties had been making preparations for an election to take place from 1939 and by the end of this year, the following candidates had been selected;