The faceoff between the United States and Jamaica ended in a victory for the US by just 0.03sec, and set up 200m champion Allyson Felix for a possible three gold medals at the championships.
The American squad of Lauryn Williams, Felix, Mikele Barber and Torri Edwards clocked 41.98sec, bettering their world leading time from the morning heats.
In the individual events, Jamaica had taken the 100m through Veronica Campbell while the US replied through Felix at 200m. So this was the decider, and appropriately it was a battle to the line.
Anchor for the US, Torri Edwards, who had been so disappointed with her fourth place in the 100m and 200m finals, was to gain some measure of revenge, lifting her arms high in celebration as she crossed the line.
Closing fast and almost catching her American prey was Campbell, who had triumphed by an even smaller margin in that final.
Here, Campbell had taken over a good 5m down, but she ate into Edwards’ lead and while the American leant back to take the applause of the packed Nagai Stadium, Campbell was leaning forwards for a victory that she almost pulled off.
Taking silvers with Campbell to match their national team's achievement in this event in 1995, 1997 and two years ago were Sheri-Ann Brooks, Kerron Stewart, Simone Facey.
Behind there was an almighty scrap for third between Britain, Russia and Belgium.
Kim Gevaert has had a good season and in Osaka she reached a World final for the first time in her career, coming within 0.01 of her best mark of 11.04 when she finished fifth.
After Olivia Borlee, Hanna Marien and Elodie Ouedraogo had run the first three-quarters of the lap, Gevaert was let loose.
Taking the baton behind Russia’s Yevgeniya Polyakova and Britain’s Joice Maduaka, she had yet another inspired run, taking metres out of them both, and capturing bronze in a national record of 42.75 for Belgium's first medal of the championships.
Osaka 2007 News Team/mb