Donald Trump has won the Republican presidential primary in New York while Hillary Clinton has triumphed in the Democratic race.
With the majority of votes counted, Mr Trump looks set to extend his lead over rivals Ted Cruz and John Kasich.
Meanwhile Democratic hopeful Mrs Clinton, a former senator for New York, is on course for a resounding victory over Brooklyn-born Bernie Sanders.
Wins will put Mrs Clinton and Mr Trump closer to securing their nominations.
With almost 95% of the results in, Mr Trump is leading with just over 60% of the vote while Mrs Clinton has just under 58%.
New York primary results
US networks projected that Mr Trump had won in his home state barely seconds after the polls closed at 21:00 EDT (01:00 GMT).
Speaking at Trump Tower in Manhattan, he said: "I have to say to the people that know me the best - the people of New York - when they give us this kind of a vote it's just incredible."
He said he was going to get more delegates than "anyone projected even in their wildest imaginations".
The big question is whether the billionaire businessman will make a clean sweep of all 95 Republican delegates at stake in New York by earning the majority of votes.
This would reduce the chances of a contested nomination at the Republican party convention in July.
A new-look Trump has a chance - by Anthony Zurcher, BBC North America reporter
Donald Trump needed a commanding victory, and he got it. Although the results in the state's 29 congressional districts - which allocate three convention delegates apiece - have yet to be finalised, it appears likely that Mr Trump will claim the lion's share of the 95 delegates at play.
Perhaps even more importantly, however, is the new, restrained Donald Trump on the campaign trail in the past few days. Gone are the incendiary tweets bashing his opponents (and their spouses). Instead on Tuesday night the candidate gave a short speech hammering home his economic message, emphasising his delegate and vote lead, and laying the groundwork to argue that he should be the party's nominee even if he doesn't win the 1,237 delegates necessary to claim the nomination outright.
Mr Trump recently brought in several experienced political hands to manage his campaign after a turbulent few weeks. If this new demeanour is part of the change they have inspired, Mr Trump could prove to be a more formidable opponent not just at the ballot box in upcoming primaries but in the contest to win over those in the party still deeply suspicious of his candidacy.
"Tomorrow, we go back to work," Mr Trump said during his victory speech. It was a very un-Trump-like line - and something that should have his opponents very concerned.
Claiming her win, Mrs Clinton told supporters her campaign for the nomination was "in the home stretch and victory is in sight".
"New Yorkers, you've always had my back and I've always tried to have yours," she said. "Today together we did it again and I am deeply, deeply grateful."
It has been a fierce campaign in the state, with the leading candidates using their local ties to attract voters.
The Democratic campaign has turned increasingly negative, with Mrs Clinton and Mr Sanders trading barbs about their qualifications.
But following the latest result in the race for the Democratic nomination, Mrs Clinton said there was "much more that unites us than divides us".