So far, so good for the defending champion U.S. men's team, which opened Olympic play by sweeping Serbia behind Matt Anderson's 18 points.
Captain Clay Stanley added 13 points in the 25-17, 25-22, 25-21 victory at Earls Court.
Also, Bulgaria swept Britain, 25-18, 25-20, 26-24, and Russia defeated Germany 31-29, 25-18, 25-17. Australia, coached by Jon Uriarte, lost to Argentina 25-21, 25-22, 25-20. Son Nicolas Uriarte is a setter on the Argentine team.
In the late matches, Poland defeated Italy 21-25, 25-20, 25-23, 25-14, and Brazil swept Tunisia 25-17, 25-21, 25-18.
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Zara Phillips, the granddaughter of Queen Elizabeth II, wowed the home crowd and a few relatives in her Olympic equestrian debut.
The 31-year-old Phillips registered a slight mistake on her appropriately named horse, High Kingdom, and earned 46.1 penalty points at Greenwich Park, placing her 24th out of 74 riders with two disciplines to go in the eventing dressage competition.
Her grandfather, Prince Philip, the Duke of Edinburgh, and her mother, Princess Anne, were in the VIP seats as Phillips put High Kingdom through the paces of a standard dressage test to demonstrate the horse's obedience.
Peter Varellas had three goals to lead the United States to an 8-7 victory over Montenegro.
U.S. captain Tony Azevedo scored with less than a minute to play, but Vladimir Gojkovic answered 10 seconds later to pull back within a goal.
Montenegro then had possession with 17 seconds to play but couldn't get off a shot before time expired.
The win puts the U.S., which has 10 players from the squad that took silver four years ago in Beijing, in a three-way tie for the Group B lead.
The favored Serbs handed Hungary its first loss in men's Olympic water polo in 12 years, beating the three-time defending champion 14-10. Romania posted a 13-4 victory over Britain.
In Group A, Croatia beat Greece 8-6, Spain opened with an easy 14-6 victory over Kazakhstan, and Alex Giorgetti scored twice to lead 2011 world champion Italy past Australia 8-5.
Scattered showers sent fans at the picturesque Horse Guards Parade scurrying for shelter during the second day of the beach volleyball tournament, dampening what had been a festive mood but not deterring the second half of the field from making its 2012 Games debut.
Emanuel, a five-time Olympian and defending world champion from Brazil, teamed with Alison to beat Clemens Doppler and Alexander Horst 19-21, 21-17, 16-14.
Elsa Baquerizo McMillan and Liliana Fernandez Steiner of Spain also rallied, edging Marleen van Iersel and Sanne Keizer of the Netherlands 14-21, 21-16, 15-11.
Defending gold medalists Todd Rogers and Phil Dalhausser of the United States, and the No. 2 American women's team, April Ross and Jennifer Kessy, each won in straight sets.
Britain, Ireland and the revitalized American team are perfect so far.
Jose Ramirez and Errol Spence won their opening bouts to move the U.S. to 4-0, while Freddie Evans and Josh Taylor rode the home crowd's raucous cheers to a 3-0 start for Britain. Welterweight Adam Nolan then added a win in the late session, pushing Ireland's record to 3-0.
Welterweight Custio Clayton also notched Canada's first Olympic win in eight years on an eventful day at ExCel.
Pau Gasol had 21 points and 11 rebounds to lead Spain to a 97-81 victory over China in their Olympic men's opener.
Spain got off to a slow start and had a 19-17 lead at the end of the first quarter. But it went on a 7-0 run in the second quarter to grab a cushion and was never seriously challenged the rest of the game.
Yi Jianlian of the Washington Wizards had 30 points and 12 rebounds for China.
Argentina kicked off its quest for a third straight men's basketball medal with a 102-79 victory over Lithuania. Luis Scola scored 32 points, and Manu Ginobili had 21 points, 10 rebounds and six assists.
Powerhouse Spain was eliminated, Brazil and Japan wrapped up spots in the quarterfinals and host Britain is back on track with one round of qualifying matches to go in the men's tournament.
Spain was hoping to add Olympic gold to the World Cup and European Championship titles held by the country's full national team. But it lost 1-0 to Honduras and is without a goal in the tournament heading into its last game against Morocco on Wednesday.
Neymar set up two goals and scored from a free kick to help Brazil beat Belarus 3-1, and Japan forward Kensuke Nagai had an 84th-minute goal to secure a 1-0 win over Morocco.
Britain posted an emphatic 3-1 victory over United Arab Emirates that knocked the Middle Eastern team out of the tournament. Mexico rebounded from a first-round loss by beating Gabon 2-0. Two-time Olympic champion Uruguay lost 2-0 to Senegal. Egypt played to a 1-1 draw against New Zealand, while South Korea beat Switzerland 2-1.
Wu Minxia and partner He Zi won the first diving gold medal of the Olympics, moving China one step closer to a sweep of the eight events in London.
They led throughout the five-dive round and totaled 346.20 points in the 3-meter synchronized event.
Abby Johnston and Kelci Bryant finished second with 321.90 points, ending America's diving medal drought that extended to the 2000 Sydney Games. It was the first Olympic synchro medal for the U.S.
China won seven of eight golds as the host country four years ago in Beijing and swept the golds at last year's world championships in Shanghai.
Emilie Heymans and Jennifer Abel earned the bronze with 316.80 for Canada's first medal of the games.
Ding Ning and Li Xiaoxia of China won their opening matches, beginning a road that is expected to bring one of them Olympic gold in women's singles.
Li, seeded No. 2 in the tournament, ended the dream of American 16-year-old Ariel Hsing, struggling to win in six games against the upstart Californian.
Billionaire Bill Gates arrived just before the match to lend Hsing support. Hsing calls him "Uncle Bill," and Warren Buffett "Uncle Warren," friendships she struck up in the past few years attending shareholder meetings of Berkshire Hathaway.
British star Ben Ainslie, trying to become the greatest Olympic sailor ever, finished second to Denmark's Jonas Hoegh-Christensen in the first two races on Weymouth Bay.
Hoegh-Christensen had a perfect day thanks to strong starts, leading at every mark in both races.
Ainslie is trying to win his fourth straight gold medal, and fifth straight medal overall, which would make him the most successful Olympic sailor ever.
South Korea won the Olympic gold medal in women's team archery for the seventh straight time.
Ki Bo-bae, Lee Sung-jin and Choi Hyeon-ju hugged and pumped their arms after their 210-209 victory over China. Japan took bronze for its first medal ever in women's archery.
Marianne Vos of the Netherlands won the gold medal in the women's road race in a rain-drenched sprint, leaving Britain's Elizabeth Armitstead with silver and the host country's first medal of the London Olympics.
Vos, the former world champion, made a daring move past Russia's Olga Zabelinskaya to emerge from the three-rider breakaway. Zabelinskaya won bronze after a frantic finish through a driving rain that was reminiscent of four years ago in Beijing.
Aron Szilagyi of Hungary won the Olympic gold medal in the men's individual saber by defeating Diego Occhiuzzi of Italy 15-8 after the top four seeds all stumbled out before the semifinals.
Nikolay Kovalev of Russia earned bronze with a 15-10 victory over Rares Dumitrescu of Romania.
The Netherlands took its first step toward retaining the Olympic women's field hockey gold, beating newcomer Belgium 3-0. Argentina lived up to its reputation as one of the tournament favorites by dominating South Africa 7-1.
Kim Lammers scored twice in her Olympic debut for the Netherlands. Lammers is the most-capped Dutch player, but she was not selected for the Athens 2004 team and a knee injury forced her to miss the Beijing Olympics.
China, the 2008 silver medalist, beat South Korea 4-0, and New Zealand defeated three-time champion Australia 1-0 in the opening match of the tournament.
In the day's last match, Germany beat the United States 2-1, holding off a strong second-half performance by the Americans.
Britain, considered a strong outsider, scored four first-half goals against Japan then relaxed in a goal-less second half.
An Kae Um won North Korea's first Olympic gold medal in London in the women's 52-kilogram category, and Lasha Shavdatuashvili of Georgia took the men's 66-kilogram category.
It's Shavdatuashvili's first Olympic medal. An won silver at Beijing.
Asian Games champion Chen Long of China reached the final 16 in the Olympic competition by defeating Boonsak Ponsana of Thailand 21-12, 21-17.
Former No. 1 Lee Hyun-il of South Korea, who was fourth at the Beijing Olympics, beat Rodrigo Pacheco Carillo of Peru in two games.
Other winners included: No. 6 seed Sho Sasaki of Japan and ninth-seeded Simon Santoso of Indonesia.
All the seeded women's players in action won, led by third-seeded Li Xuerui of China and No. 4 Saina Nehwal of India.
Defending champion France defeated Britain 44-15 in their opener, dashing the host's hopes for a decent performance in a sport that lacks the popularity of football and rugby in Britain.
Ivan Cupic scored eight goals and two-time Olympic champion Croatia beat South Korea 31-21 in the men's tourney.
Spain, Iceland, Sweden and Denmark also won.
Zulfiya Chinshanlo of Kazakhstan won the Olympic gold medal in women's 53-kilogram.