1908 - Bible protest
USA's Forrest Smithson carried a bible while posing for a picture after winning gold in 110m hurdles - in protest at having to race on a Sunday.
1908 - 400m final re-run
Great Britain's Wyndham Halswelle winning gold in the re-run of the 400m in London. He was the only runner - the other three were all Americans who pulled out when one of them was ruled to have blocked Halswelle in the original final.
1912 - Jim Thorpe loses gold medals
USA's Jim Thorpe on his way to winning a gold medal in both the decathon and pentathlon - he was stripped of them when it was found he had played two seasons of semi-pro basketball. In 1983, his medals were posthumously restored.
1932 - Gender controversy
Stella Walsh, left, (here with Mildred 'Babe' Didrikson) won gold for Poland in the 100m sprint in 1932. A post-mortem on her death in 1980 found she had genitals of 'indeterminate' gender and controversy remains over retaining records she set.
2009 - Gender controversy
Caster Semenya of South Africa had her gender questioned after winning gold in the 2009 World Championships in the 800m. The handling of the case by the IAAF attracted huge criticism. She has since been cleared to compete in the 2012 Olympics.
1936 - Jesse Owens takes gold in Berlin
America's Jesse Owens, centre, taking gold for the long jump. Nazi Germany's Lutz Long, right, took silver. Adolf Hitler decided to skip his medal presentations (Owens went on to win four gold in total in 1936).
1956 - Hungarian revolution spills over
Hungary's Ervin Zadar has a bloodied face after his team and that of the Soviet Union clashed violently in the water polo semi-finals. The Soviet Union had invaded Hungary a few weeks earlier and it was the year of the Hungarian Revolution.
1968 - Mexico City massacre
Student and civilian protestors were massacred in Mexico City by government-directed snipers ten days before the Olympics there. It has been claimed that some of the forces were used as security guards at the Games.
1968 - Black Power salute
USA athletes Tommie Smith, centre, and John Carlos stare downward during the playing of the Star Spangled Banner and give the Black Power salute with gloved hands as a civil rights protest.
1972 - Munich's Black September
A hooded member of the Palestinian terrorist group which held members of the Israeli Olympic team hostage in the Munich Olympic village - they killed 11 athletes and coaches.
1972 - Basketball gold medal controversy
USA basketball team players enjoy a brief moment of elation when they thought they had beaten the Soviets, but the referee reset the clock by three seconds and the Soviet Union scored a final goal to win the game 51-50.
1980 - Mass boycott of Moscow Olympics
Soviet athlete Sergei Belov in the opening ceremony. A number of teams boycotted the ceremony to protest Soviet intervention into Afghanistan - and many boycotted the Games themselves.
1980 - The 'bras d'honneur'
Poland's Wladyslaw Kozakiewicz gave the booing and jeering Soviet crowds the 'bras d'honneur' (equivalent to giving them the finger) when he won gold in the pole vault. The Polish government later claimed his gesture was an involuntary muscle spasm.
1984 - Mary Decker and Zola Budd collide
This sequence shows USA's Mary Decker falling as UK's Zola Budd (No.151) looks at her in the 3,000m in LA. An inquiry found Budd not responsible for the fall and Decker later confirmed that the case.
1988 - Boxing gold controversy in S. Korea
Korea's Park Si-hun, left, won gold in the light middleweight against USA's Roy Jones in the Seoul Olympics. It turned out Jones had landed 86 punches to Park's 32 and two of the three judges at the bout were later banned for life.
1996 - Atlanta Olympics bombing
Lone terrorist Eric Robert Rudolph killed 2 people in a bombing at the Centennial Olympic Park which he hoped would embarrass the US government. He was protesting about the provision of abortion in the USA.
1996 - Ireland's 'golden girl'
Michelle Smith won three gold swimming medals and a bronze at Atlanta - immediately after a US swimmer accused Smith of doping. Smith passed drug tests at the time but received a four-year ban for tampering with a urine sample in a random test in 1998.
2000 - Marion Jones's contested five golds
USA athlete Marion Jones won 5 golds at the Olympics including with the 4 x 400m relay team. She admitted taking performance-enhancing drugs after a long inquiry and was stripped of her medals in 2007. Some of her relay team-mates also lost theirs.
2004 - Athens marathon runner disrupted by Irish 'priest'
Defrocked Irish priest Cornelius Horan grabs Vanderlei de Lima of Brazil three miles from the end of the men's marathon event. De Lima had been leading and finished third.
2004 - The doped-up horse
Waterford Crystal, the horse of Ireland's Cian O'Connor, tested positive for banned drugs and their Athens gold medal for showjumping was taken back by the IOC.
2008 - Clearing up for Beijing Olympics
China was accused of clearing out poor, homeless and migrant people to make way for construction of their Olympic venues.
2008 - Wrestler rejects bronze
Sweden's Ara Abrahamian was so incensed by a judging decision in his Greco-Roman wrestling final that he left his bronze medal on the mat in the awards ceremony. He was stripped of his rejected medal by the IOC.
2008 - Referee attacked
Cuba's Angel Valodia Matos, left, kicked and punched match referee Chakir Chelbat after he lost his bronze medal match in taekwondo.