American Michael Phelps earned his fifth gold medal of the games, but announced that he will not go for an eighth overall medal on Saturday.
Phelps won the gold medal Friday in the 100-meter butterfly with an Olympic record time of 51.25 seconds. American Ian Crocker took the silver in a time of 51.29. Andriy Serdinov of Ukraine won the bronze in 51.36.
Phelps later announced that he would not take part in the 4 x 100-meter medley relay Saturday, ceding his place to Crocker.
American Gary Hall proved that age is no barrier when he won his second straight 50-meter freestyle Olympic crown, triumphing by the narrowest of margins - one-hundredth of one second. Hall, who turns 30 next month, managed to touch the wall first in 21.93 seconds. Croatian Duje Draganja was second with a time of 21.94. South African Roland Schoeman was third in 22.02.
Kirsty Coventry of Zimbabwe won the gold medal in the 200-meter backstroke with a time of 2:09.19. Ai Shibata of Japan won the gold medal in the 800-meter freestyle with a time of 8:24.54.
In cycling, Australia's Anna Meares became the first woman to beat the 34-second mark over 500 meters to win the track cycling time trial gold medal. Chris Hoy of Britain won the gold medal in the men's 1-kilometer time trial with an Olympic-record time of 1:0.711 minutes.
China continued its dominance of table tennis when Wang Nan and Zhang Yining won gold in women's doubles, defeating Lee Eum-sil and Seok Eun-mi of South Korea. China's Guo Uue and Niu Jianfeng won the bronze.
In badminton, South Koreans Kim Dong-moon and Ha Tae-Kkon defeated compatriots Lee Dong-soo and Yoo Yong-sung to win the gold medal in the Olympic men's doubles badminton.
In archery, South Korea beat China, 241-240, to win the gold medal in women's team archery. Taiwan won the bronze medal.
Japan continued its dominance of the judo competition when Keiji Suzuki of Japan won the gold medal in the men's 100-kilogram-and above category.
Maki Tsukada of Japan won the gold medal in the women's 78-kilogram and above category in judo. Japan finished the Olympics competition with a record eight gold medals. Belarus, China, Georgia, Germany, Greece and South Korea won one gold each.
Team USA member Matthew Emmons won gold in the men's 50-meter prone rifle shooting competition. Russian Lioubov Galkina took first in the women's 50-meter, three-positions rifle competition.
Slovakian twins Peter and Pavol Hochschorner easily repeated as Olympic champions in the two-man canoe slalom. Benoit Peschier, 24, of France won the kayak slalom event with an overall time of 187.96 seconds.
Pawina Thongsuk, from Thailand edged out Natalia Zabolotnaia of Russia on lower body weight in the 75-kilogram category, the Thai being more than four kilos lighter. The Russian went away with two new world records but only a silver medal.
Italian Ivano Brugnetti won the Olympic gold medal in the men's 20-kilometer race walk, covering the distance in 1 hour, 19 minutes and 40 seconds. In the athletics night session, Ethiopia's world record holder Kenenisa Bekele won the 10,000 meters title. Veteran countryman Haile Gebrselassie, who was trying to win the race for a third time, finished fifth.
The United States leads the medal table with 17 gold medals and 40 overall. China has 15 golds and 36 overall while Japan has 19 total medals including 12 gold. Australia, Russia and Italy follow in the standings.