Six world records in the evening session at the world championships in the Foro Italico in Rome took the total for the meet to 35.
At the last world championships in Melbourne in 2007, 15 world records were broken in total and with two days of competition remaining, this number has already been more than doubled.
In the evening session on Friday the first four swims saw Britta Steffen breaking the women's 100m freestyle record, American Aaron Peirsol winning gold in the men's 200m backstroke in world record time and in the semi-finals of the women's 50m butterfly Marleen Veldhuis and Therese Alshammer taking the world record in consecutive heats.
Serbian Milorad Cavic later broke the men's 100m butterfly world record, before a short lull in setting world records was broken in the final event of the evening by the US men's 4x200m freestyle relay team.
Although Michael Phelps was again beaten by Germany's Paul Biedermann in the opening leg of the relay, the Americans then took control of the race.
Anchor man Ryan Lochte came under pressure from Russia, he managed to hold on to give the US victory in 6:58.55, just one hundredth of a second under their old world record.
For Lochte it was already the third gold medal. He also has a bronze, making him the most successful swimmer at the competition.
Russia took the silver medal, .60 seconds off the pace, while Australia won the bronze with a time of 7:01.65.
Phelps said that when he had seen that he was swimming against the man who beat him in the 200m freestyle in the waiting room, he was not too concerned.
"I think I tried to control it a bit and not just jump in on the first 100. I was not as fast as I would have liked to have been."
He said that he had seen in the morning that Biedermann had led the German relay team. "I thought that I would anchor ours, but the coach said from the beginning that I would lead."
Steffen, who last year took two golds in Beijing, won the one medal that has thus far eluded her when she won the women's 100m freestyle, breaking the world record for the second time in five days.
The 25-year-old won the gold in a time of 55.07, beating the old best mark of 52.22, which she established Sunday as the opening swimmer of the German women's 4x100m freestyle relay swimmer.
Britain's Fran Halsall took the silver medal with a time of 55.87, while Libby Trickett of Australia won the bronze medal with a time of 55.93.
"I am really, really happy. Now anything can happen and I can accept it," Steffen said as she was hugging members of the German technical staff.
In the very next race Peirsol broke his own men's 200m backstroke world record, winning gold in a time of 1:51.92. His old record stood at 1:53.08.
Japan's Ryosuke Irie won the silver medal in 1:52.51, while Peirsol's compatriot Ryan Lochte, who earlier in the week won the 200m individual medley, took the bronze 1.90 off the pace.
Peirsol, who sensationally was eliminated in the semi-finals of the 100m backstroke said that could have worked in his favour. "I was more rested than I thought, it was probably a blessing in disguise.
"Winning the gold medal makes up for it. I moved on after they swam the finals. I was very motivated for this race."
Hungarian outsider Daniel Gyurta took the gold medal in the men's 200m breaststroke, winning in a time of 2:07.64, beating American Eric Shanteau by just one hundredth of a second.
Australian Christian Sprenger, who on Thursday broke a world record in the event, shared bronze with Lithuanian Giedrius Titenis.
There was also an unexpected gold medal for Serbia in the women's 200m breaststroke as Nadja Higl came through on the last 50m to move from third into first, winning the gold medal in a time of 2:21.62.
The silver medal went to Canadian world record holder Annamay Pierse in a time of 2:21.84, while Austrian Mirna Jukic won the bronze medal .35 seconds off the pace.
There was further joy for Serbia as Cavic, who had earlier in the day offered to buy Michael Phelps an all-polyurethane bodysuit, broke the world record in the semi-finals of the 100m butterfly in a time of 50.01 seconds.
Phelps had the second-fastest time in 50.48.
Zimbabwean Kirsty Coventry, who is still waiting for her first medal of the championships, led the field into the final of the women's 200m backstroke with a championship record time of 2:05.86, beating Russian Anastasia Zueva by 1.14 seconds.
In the semi-finals of the women's 50m butterfly Dutchwoman Veldhuis broke her own world record in a time of 25.28, taking seven hundredths of a second off her old best mark.
But that time was beaten in the second semi-final by Sweden's Alshammar, who came close to breaking the 25-second barrier. She won her heat in a time of 25.07 to go through to Saturday's final.
In the semi-finals of the men's 50m freestyle French world record holder Frederick Bousquet managed to break the championship record when he qualified for the finals in a time of 21.21.
In the first heat, Croatian Duje Draganja had already broken the championship record with a time of 21.29, only to see Boiusquet go even faster.
Brazilian Cesar Cielo Filho, who on Thursday won the men's 100m freestyle in world record time, went into the final with the fourth-fastest time.
The championships, which started on July 17, end on Sunday.