The membership was set by the 2004 federal election on June 28, 2004, and it changed only somewhat due to resignations and by-elections, but due to the seat distribution, those few changes significantly affected the distribution of power.

It was controlled by a Liberal Party minority under Prime Minister Paul Martin and the 27th Canadian Ministry.

The Official Opposition was the Conservative Party, led by Stephen Harper.

The party standings as of the election and as of dissolution were as follows: Important bills of the 38th parliament included: Complete list of bills In early 2005 Ontario Member of Parliament (MP) Belinda Stronach crossed the floor to the Liberal Party after running for Leader of the Conservative Party of Canada, and coming in second to Stephen Harper.

She ended her public relationship with Conservative MP Peter MacKay.