Eaton needed to slash six seconds off his fastest-ever time in the 1,500 to break his world record, but ran a cautious race and finished well outside his personal best in 4 minutes, 33.59 seconds.
U.S. 1-2 triple jump. Christian Taylor won the Olympic triple-jump gold medal to go with his world title, overtaking U.S. teammate Will Claye with his fourth jump in the final.
Taylor continued his season-leading form with a best jump of 17.81 meters (58 feet, 51/4 inches). Claye won silver at 17.62 meters (57-93/4), and Italy's Fabrizio Donato, the 35-year-old European champion, took bronze at 17.48 (57-41/4).
Record 800 race. Kenya's David Rudisha did what no one else, Usain Bolt included, has been able to do in the London Games: set a world record on the Olympic track.
Rudisha won the 800 meters in 1:40.91, one-tenth of a second better than the mark he set in 2010. That makes him the first man ever to run a sub-1:41.00 time for the 800.
He has been the dominant 800-meter runner for the last three years, setting the world record three times and losing just once since 2009.
Botswana got its first Olympic medal when 18-year-old Nigel Amos took silver behind Rudisha in a world junior-record time of 1:41.73. Timothy Kitum of Kenya got the bronze in 1:42.53.
Americans Duane Solomon and Nick Symmonds finished fourth and fifth, just ahead of 18-year-old Mohamed Aman of Ethiopia, the world indoor champion who handed Rudisha his only loss in three years last September.
Going for relay gold. The United States and Jamaica reached the final in the women's 4x100-meter relay.
The Americans won their heat in 41.64 seconds, with Tianna Madison, Jeneba Tarmoh, Bianca Knight, and Lauryn Williams carrying the baton.
The Jamaicans weren't nearly as smooth. Sherone Simpson and Schillonie Calvert nearly botched the exchange between the second and third legs. With Samantha Henry-Robinson running the opening 100 meters and Kerron Stewart serving as the anchor, the Jamaicans finished in 42.37 seconds, edged at the line by Ukraine.
The final is Friday.
Semenya in final. Closing in on an Olympic medal three years after being forced to undergo gender tests, Caster Semenya of South Africa won her 800 semifinal heat in 1:57.67.
The final on Saturday will include defending champion Pamela Jelimo of Kenya, who won her semifinal.
Semenya is making her Olympic debut. She was sidelined for nearly a year while track and field's governing body decided whether to allow her to compete after she won the 2009 world title at age 18. She was tested and eventually cleared to return to action in 2010 and was the runner-up in last year's world championships.