Donald Trump has won presidential primaries in all five US states that voted on Tuesday, while Hillary Clinton took four out of five.
Mr Trump called himself the Republican "presumptive nominee" after victories in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island.
The results bring him closer to the number of delegates he needs before the party's national convention in July.
For the Democrats, Mrs Clinton was denied a clean sweep by Bernie Sanders.
Mr Sanders won the vote in Rhode Island, and vowed to fight to the end of the primaries process.