Four federal byelections — two in Alberta, two in Ontario — will be held June 30.
The Alberta constituency of Fort McMurray-Athabasca was vacated by Conservative MP Brian Jean, who stepped down in January, citing a desire to spend more time with his family.
Conservative MP Ted Menzies resigned his southern Alberta seat in the riding of Macleod in November to become president and chief executive officer of CropLife Canada, a trade association for plant-life technologies.
Trinity-Spadina became vacant when New Democrat Olivia Chow resigned to run for mayor of Toronto.
And in Scarborough-Agincourt, Liberal stalwart Jim Karygiannis stepped down to run for a seat on Toronto city council in a ward that overlaps much of the federal riding.
However, Prime Minister Stephen Harper did not call a byelection for the Ontario riding of Whitby-Oshawa, left without an MP upon the recent death of Conservative Jim Flaherty, the former finance minister.
The byelection announcements come amid a flurry of behind-the-scenes preparation and nomination meetings for a general election next year.