They have gained three new seats from the Ulster Unionist party in Strangford, East Londonderry and North Belfast.
Although they lost the South Antrim seat to the Ulster Unionists their wins have been more dramatic than this loss.
The changes are a body blow for the UUP leader David Trimble.
He narrowly took his own constituency, Upper Bann, but was only 2,000 votes or so ahead of the DUP.
In 1997 the DUP lay in fourth place in Upper Bann and Mr Trimble was 15,000 votes ahead of them.
Throughout his acceptance speech Mr Trimble was shouted down by DUP opponents.
There were repeated calls of "traitor" as Mr Trimble criticised the reception he and his party workers had received.
When he left the count centre in Banbridge a protestor threw handfuls of clay at him as he was given a heavy police escort to his car.
In a BBC interview, Mr Trimble said those Ulster Unionists who had lost their seats had "fought good fights".
"Obviously we very much regret the fact that we have lost those seats, but on the other hand there is very much congratulations to Sylvia and David Burnside," he said.
"The Agreement changed the political landscape completely - that is indisputable.
"In the assembly election that followed, the Ulster Unionist Party got 21.7% of the vote.
"On this occasion we increased that to 26.8%."
Mr Trimble described it as "an extremely good result".
The results seem likely to make agreement between Northern Ireland's two communities even more difficult.
Iris Robinson took the Strangford constituency with a majority of about 1,000 votes.
In 1997 she was defeated by 6,000 votes.
" This is one in the eye for the pan-nationalist front and for David Trimble "
Nigel Dodds, DUP
Mrs Robinson said hers was an "historic victory" and her door was open to all her constituents whether or not they had voted for her.
Earlier Gregory Campbell took the East Londonderry seat from the Ulster Unionist Party.
Its candidate, the sitting MP Willie Ross, was defeated by almost 2,000 votes.
"There is a God in heaven," said Mr Campbell about his win.
Earlier Nigel Dodds of the DUP captured the North Belfast seat with a landslide majority.
The vote of his opponent Cecil Walker, the sitting MP, was down by about 40%.
"This is one in the eye for the pan-nationalist front and for David Trimble," said Mr Dodds.
SDLP vote collapse
He added that it was also a victory for those who didn't want "gunmen in government".
The DUP leader Ian Paisley went further: "Nigel Dodds whipped them, whipped them, whipped them," he said of the UUP.
He took his own seat in North Antrim with an increase in his majority of about 3,000.
The party's Deputy Leader Peter Robinson regained East Belfast.
There were gains for the UUP in North Down and South Antrim.
Lady Sylvia Hermon took the North Down seat from the UKUP leader Bob McCartney.
In a bid to oust Mr McCartney the Alliance Party had stood down in favour of Lady Hermon.
She became the first woman MP to be elected in Northern Ireland since Bernadette Devlin in the 1960s.
In South Antrim the UUP overturned their by-election defeat of last September.
David Burnside won the seat back from Willie McCrea of the DUP with a majority of about 1,000.
Two of the UUP's anti-Agreement MPs Rev Martin Smyth and Jeffrey Donaldson were returned to their constituences in South Belfast and Lagan Valley.
Meanwhile on the nationalist side Sinn Fein has overtaken the moderate SDLP as the bigger party.
It won the West Tyrone and Fermanagh seats from the UUP with Pat Doherty and Michelle Gildernew.
Sinn Fein now has four seats to the SDLP's three.
The SDLP chairman Mark Durkan has admitted it was a disappointing day for his party.