Australia's Christian Sprenger gained revenge for his defeat in last year's Olympic final when he won the men's 100m breaststroke gold at the swimming world championships on Monday.
South Africa's Olympic champion Cameron van der Burgh, who edged Sprenger into second in the Olympic final, was second and Brazil's Felipe Lima third.
Sprenger clocked 58.79secs, ahead of Van der Burgh, the world record-holder, who was just 0.18secs behind, while Lima touched the wall at 59.65.
Exactly a year to the day after the Olympic final, the 27-year-old Sprenger took his revenge as he overhauled the South African, the halfway leader, on the return lap.
Van der Burgh's world record of 58.46secs was under threat at one point as Sprenger accelerated in the final 25 metres to win Australia's first gold in Barcelona.
"To finally have the Australian anthem played for me is an amazing feeling," said Sprenger.
"After a swim I couldn't be prouder of, capped off a really nice two days for me."
Having been blighted by injury since his Olympic triumph, Van der Burgh said he was happy with silver.
"This year been a lot of hiccups and setbacks: first with a shoulder injury then a knee injury," he said.
"I had a couple of months off after the Olympics and think the outcome today was really deserved.
"Christian deserves the gold and I was happy to take the silver with the work I've put in."
Lima was delighted with his first major medal.
"I dropped below one minute for the first time and in the final I put my life and soul into it again, so I'm really, really happy with the result," said the 28-year-old.
There was no defending champion in this race as 2011 title-holder Alexander Dale Oen of Norway, a close friend of Van der Burgh, died in April last year.
The 26-year-old suffered a heart attack, due to a previously undetected coronary disease, while at a training camp with his national team in the United States.
"I didn't have thoughts of him today. Alex passed away almost a year and a half ago now so it has been quite a while," said Van der Burgh.
"I dedicated the race in London to him and I think he definitely helped me through that, but I think Alex is the kind of person who would encourage that.
"I think if we thought about him every race and every race we mourned him, you wouldn't be living in the future, you would be living in the past which is not the kind of person that he was."