Fina World Championships
Date: 17 July-2 August (swimming from 26 July) Venue: Rome
Live/highlights on BBC Two, Red Button and BBC Sport website
Replay - Phelps chases down Cavic
Michael Phelps cut an emotional figure after beating rival Milorad Cavic in the 100m butterfly at the World Championships in Rome.
American Phelps won in a world record 49.82 seconds to answer the taunts of Serbia's Cavic ahead of the duel.
"There was a lot said leading up to that race," said Phelps, who beat Cavic by a hundredth of a second at last year's Beijing Olympics.
"That (my reaction) was all the emotion coming out."
The American, who has also won gold in the 200m butterfly and two relays this week added: "It probably won't stop for a couple of days."
Phelps became the first man to go under 50 seconds with his swim, while Cavic also broke the barrier with a time of 49.95.
Cavic had led at the turn with Phelps in fourth but the American showed his strength in the final 50m - just like the final in Beijing - to win his fourth gold of the meet.
Phelps's reaction to the win as he flexed his arms, punched the air and barely acknowledged his rival showed his delight and anger to the Serbian's comments in the build up to their rematch.
When he won he appeared he was trying to make a statement and he certainly did
Cavic had offered to buy his rival one of the 100% polyurethane suits that he wears and which are considered faster than the 50% polyurethane suit worn by Phelps.
And Cavic, who always maintained that he actually touched first in Beijing, had gone into the final with plenty of confidence after breaking Phelps's world record with a time of 50.01 in the semi-finals.
Phelps responded in emphatic fashion and tugged at his supposedly slower Speedo LZR suit at the end, but he insisted: "It doesn't matter about the suit, it's about how you train.
"I set it up perfectly, it was exactly what I wanted to do.
"I had to be out in that first 50m within striking distance and I went out in 23.3sec, that's the fastest I've been out in, I haven't been within half a second of that. It's really gratifying."
His coach Bob Bowman added: "He showed speed he's never had before. It was perfectly done."
Cavic was a more diplomatic figure after the race compared to before and said: "Everybody wants to win but it didn't happen.
"I turned at the 50m and saw that he was very near and thought 'oh-oh he's going to be coming back'. To my surprise I was very strong towards the end, he was just a little bit stronger.
"It was a great race and I lost to the best in the world and that's OK with me.
"There is no tension but when he won he appeared he was trying to make a statement and he certainly did."