The United States have won the women's 4x100 metres relay in a world record of 40.82 seconds at the Olympic Stadium.
The team of Tianna Madison, Allyson Felix, Bianca Knight and Carmelita Jeter raced away from their closest challengers Jamaica to take gold.
The Jamaicans ran a national record of 41.41, but still finished well adrift, while Ukraine took the bronze.
Asli Cakir Alptekin took gold in the women's 1,500m. The Turkish athlete won a slow race in 4:10.23, finishing ahead of compatriot Gamze Bulut, with Bahrain's Maryam Yusuf Jamal third.
Britain's Lisa Dobriskey, for whom reaching the final was some achievement having battled back from potentially life-threatening blood clots on her lungs, was 10th in 4:13.02 and Laura Weightman, in her first major championship, 11th in 4:15.60.
There was more agony for American Morgan Uceny as she fell for the second major final in succession, having also hit the track at last year's World Championships in Daegu when she was one of the favourites.
Russia's Tatyana Lysenko has won gold in the women's hammer in an Olympic record of 78.18m. She led all the way through the competition, having thrown 77.56m with her first attempt, before going even further with her penultimate effort.
Poland's Anita Wlodarczyk took the silver with a final throw of 77.60m and China's Zhang Wenxiu the bronze with 76.34, while Ethiopia's Meseret Defar won the gold medal in the women's 5000m final.
Steve Lewis had to settle for joint fifth place in the pole vault with a best of 5.75m, while the Bahamas have won gold in the men's 4x400 metres relay and France's Renaud Lavillenie took gold in the men's pole vault.