The Conservatives have gained the Vale of Clwyd from Labour, securing 39% of the vote.
James Davies saw off the challenge of Labour candidate Chris Ruane who previously held the seat, with a majority of just 237.
The Conservatives have gained Brecon and Radnorshire from the Liberal Democrats, securing 41.1% of the vote.
Christopher Davies saw off the challenge of Lib Dem candidate Roger Williams who previously held the seat, with a 5,102 majority.
Unlike his namesake Mark Williams, Roger Williams has proved unable to resist the anti-Lib Dem tide. He saw his vote drop by 18% as the Conservative chris Davies took the seat, with Labour also well up as the tradition of tactical voting in Brecon and Radnorshire broke down.
The Conservatives have held Montgomeryshire, securing 45% of the vote.
Glyn Davies saw off the challenge of Liberal Democrat candidate Julie Dodds, with a 5,325 majority.
By Nick Hartley, Brecon & Radnorshire
Welsh Liberal Democrat sources have conceded they are set to lose their hold on Brecon & Radnorshire to the Conservative party in one of Wales' most closely contest seats.
The mid-Wales constituency has been under the leadership of Roger Williams since 2001 and a party seat since 1997, but it is on course to see a 3,747 majority overturned in favour of Welsh Conservative candidate Chris Davies.
A loss would heap further angst on what exit polls have suggested will be painful night for the Liberal Democrats right across Britain.
The result is expected around 0300 BST.
Montgomeryshire had long been a Liberal stronghold. They had held it for 99 years when they lost in it 1979 to the Conservatives and managed to snatch it back in 1983 despite that year's Conservative landslide. The Conservative victory last time was blamed by the Lib Dems on Lembit Opik being just too controversial for Mid Wales tastes. But Glyn Davies, who's a former chairman of Mid Wales Development, now appears well dug in.