With 12 states and one territory voting, both Clinton and Trump won most of the states on the biggest day of the race towards collecting their parties nomination.
Trump has won seven states, whereas his closest rival thus far Ted Cruz won three. Senator Marco Rubio secured just one state.
Meanwhile, senator Bernie Sanders won four states, including the state he represents, Vermont.
In her victory speech, Clinton, seemingly eyeing a run-off with Trump, said: "The stakes in this election have never been higher and the rhetoric we're hearing on the other side has never been lower."
And Trump was unambiguous in his speech in Florida: "Once we get all this finished, I'm going after one person - Hillary Clinton."
The day is huge as it designated almost half of the delegates needed on the Republican side of the race to become the nominee, while near a third of the delegates needed for the Democrat nomination were up for grabs.
It's also the first day of national judgement for all candidates, as states across the country vote.