By Andrew Black
Political reporter, BBC Scotland news website
A Westminster by-election is being held in the seat of Glasgow North East in the wake of sitting MP Michael Martin's resignation from parliament and as Commons speaker.
Here, the BBC Scotland news website looks at the background and results of recent key UK by-elections in Scotland.
FRIDAY 7 NOVEMBER, 2008 - GLENROTHES
Result: Labour hold Majority: 6,737 Swing: 4.9% from Labour to SNP.
This by-election, in the seat neighbouring Gordon Brown's constituency, was held after the death of sitting MP John MacDougall.
Labour held the seat with a comfortable majority in the face of a strong SNP challenge - the Tories and Lib Dems came some way behind and both candidates lost their deposits.
Labour victorious in Glenrothes
By-election breakdown: Lindsay Roy (Labour) 19,946; Peter Grant (SNP) 13,209; Maurice Golden (Con) 1,381; Harry Wills (Lib Dem) 947.
Friday 25 July, 2008 - Glasgow East
Result: SNP gain Majority: 365 Swing: 22.5% from Labour to SNP
Labour lost one of its safest Scottish seats when the SNP overturned a majority of 13,507 to win by just a few hundred votes.
The Tories came third in the contest, sparked by the resignation of sitting MP David Marshall on health grounds, while the the Lib Dems took fourth position.
SNP stuns Labour in Glasgow East
By-election breakdown: John Mason (SNP) 11,277; Margaret Curran (Lab) 10,912; Davena Rankin (Con) 1,639; Ian Robertson (Lib Dem) 915.
Friday 10 February, 2006 - Dunfermline and West Fife
Result: Liberal Democrat gain Majority: 1,800 Swing: 16.24% from Labour to Lib Dems.
The Liberal Democrats overturned Labour's majority of more than 11,500 in the constituency, which neighbours Gordon Brown's Kirkcaldy and Cowdenbeath seat.
Willie Rennie was declared the victor with 12,391 votes in the by-election, which was called after the death of sitting MP Rachel Squire. Labour came second.
Lib Dems deliver blow to Labour
By-election breakdown: Willie Rennie (Lib Dem) 12,391; Catherine Stihler (Lab) 10,591; Douglas Chapman (SNP) 7,261; Carrie Ruxton (Cons) 2,702.
Thursday 29 September, 2005 - Livingston
Result: Labour hold Majority: 2,680 Swing: 10.22% from Labour to SNP
The Livingston by-election was called following the sudden death during a hill walking trip of the sitting MP and former cabinet minister Robin Cook.
His former election agent and trade unionist Jim Devine held the seat for Labour, but its majority fell from 13,000 at the General Election earlier that year to 2,680.
At the same time Labour also held the Holyrood seat of Glasgow Cathcart, made vacant following former MSP Mike Watson's conviction for wilful fire-raising.
Labour holds Cook's Commons seat
By-election breakdown: Jim Devine (Lab) 12,319; Angela Constance (SNP) 9,639; Charles Dundas (Lib Dem) 4,362; Gordon Lindhurst (Cons) 1,993.
Thursday 21 December 2000 - Falkirk West
Result: Labour hold Majority: 705 Swing: 16.1% from Labour to SNP
This by-election was triggered by the resignation of Dennis Canavan, who won the seat for the party but later took the constituency at Holyrood as an independent, after being excluded from Labour's candidate list.
The Labour Party fought the contest on the premise that voters should still elect a Labour successor and narrowly hung onto the seat.
Labour positive over by-election
By-election breakdown: Eric Joyce (Lab) 8,492; David Kerr (SNP) 7,787; Craig Stevenson (Con) 1,621; Hugh O'Donnell (Lib Dem) 615.
Thursday 23 November, 2000 - Glasgow Anniesland
Result: Labour hold Majority: 6,157 Swing: 6.5% from Labour to SNP
Labour easily held onto the seat, which became vacant following the death of Scotland's first first minister, Donald Dewar.
The night was a double by-election victory for Labour - Mr Dewar also held the seat at the Scottish Parliament, which went to left-winger Bill Butler with a majority of more than 6,000.
Dewar by-elections date revealed
By-election breakdown: John Robertson (Lab) 10,359; Grant Thoms (SNP) 4,202; Dorothy Luckhurst (Con) 2,188; Chris McGinty (Lib Dem) 1,630.
Friday 24 September, 1999 - Hamilton South
Result: Labour hold Majority: 556 Swing: 22.56% from Labour to SNP
Labour only just hung onto the seat after the sitting MP and then defence secretary, George Robertson, quit parliament to become Nato secretary general.
The 15,878 majority Mr Robertson achieved at the 1997 General Election was partly eroded by the SNP vote and the Scottish Socialist Party, which came third, ahead of the Conservatives and Liberal Democrats.
By-election breakdown: Bill Tynan (Lab) 7,172; Annabelle Ewing (SNP) 6,616; Shareen Blackhall (SSP) 1,847; Charles Ferguson (Con) 1,406; Marilyne MacLaren (Lib Dem) 634.
Labour scrapes home