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 wins gold in the relay (UK users only)
Michael Phelps's world championship campaign got off to a winning start on Sunday as his USA team took gold in the men's 4x100m relay.
Phelps, who won eight gold medals at the 2008 Beijing Olympics, swam the team's slowest leg as they beat Russia and France in a time of 3:09.21.
The Americans were third after Phelps's first leg, before he handed over to Ryan Lochte.
But Matt Grevers and Nathan Adrian helped them pull off a famous win.
Phleps has endured an eventful year since his Beijing heroics, suffering from injury and non-sporting related problems, most notoriously when he was photographed apparently smoking drugs.
He apologised for his behaviour but USA Swimming imposed a three-month ban.
The 24-year-old apologised for his behaviour but was banned for three months by USA Swimming, and lost a sponsorship deal in the aftermath of the affair.
Since then he has been plagued by a neck injury that forced him to withdraw from the 100m freestyle at the US trials.
And the American revealed he is still suffering from the injury and dismissed claims from defending 100m champion Filippo Magnini's he had "ducked" out of the trials.
"It was never an excuse as it was stated in the paper by one of the athletes," added Phelps. "I actually wanted to swim that race."
Phelps pondered his future during the last year, wondering whether to quit swimming.
But Phelps chose to continue and has taken the decision to dedicate himself to the pool through to the London 2012 Olympics.
As well as three relays, Phelps will also compete in the 100m and 200m butterfly and the 200m freestyle as he looks to add to his pre-Rome tally of 20 world championship medals, 17 of them gold.
And despite his recent absence from the international circuit, Phelps is looking forward to his return to action.
"I always want to win," he said. "If I have the race I want to have and someone swims faster than me then so be it. When I come into a meet I have things I want to achieve and that is all I think about."
Meanwhile, Phelps welcomed proposed changes to swimsuit rules after a number of record fell on Sunday.
World swimming governing body Fina has decided to ban controversial non-textile swimsuits from 2010, with all-textile suits and traditional briefs for men making a comeback.
"Swimming will actually become swimming again. We're all going to have the same exact suit. It's not going be an issue," said Phelps.
"It's not going to be a question of what suit we're wearing, who's wearing what. We'll see what happens over the next few months. I'm excited to see what's going to happen for the future of the sport."