The athletes had to comply with the rules: cheating and corruption were forbidden. On the first day of the games the athletes swore solemnly not to commit offences before the statue of Zeus, ‘the guardian of the oaths’, in the council house of Olympia. The same oath was sworn by their fathers, brothers and trainers. The umpires and hellanodikai attentively watched the participants during the contest. If they acted against the rules, they offended Zeus. For cheating in the games they were punished corporally, for corruption with fines.

The hellanodikai swore an oath too, by which they promised to make a fair judgement and not to take bribes. Dividing young athletes in age categories or deciding whether someone was indeed a free Greek citizen was a delicate matter, as the Greeks did not have birth certificates. Also decisions on a close fought pankration match, or on the result of a race where to runners crossed the finish almost simultaneously, were difficult. It is not unthinkable that the hellanodikai were in such cases approached by people involved who tried to influence the decision to their advantage.

The exact words of the ancient oath are not preserved. For the modern Olympics, a new oath was written, which was sworn for the first time at the games in Antwerp in 1920. The oath is sworn by one athlete and one member of the jury of the organizing state in the name of all athletes and members of the jury.  

For the athletes: 'In the name of all the competitors I promise that we shall take part in these Olympic Games, respecting and abiding by the rules which govern them, committing ourselves to a sport without doping and without drugs, in the true spirit of sportsmanship, for the glory of sport and the honour of our teams.'

For the judges: 'In the name of all the judges and officials, I promise that we shall officiate in these Olympic Games with complete impartiality, respecting and abiding by the rules which govern them, in the true spirit of sportsmanship.'