Chess players now face drug tests before entering competitions.
The game's governing body, the Federation Internationale des Echecs, wants chess to be an Olympic sport and drug-testing is compulsory for it to be considered.
Testing began at a youth tournament in Argentina last month.
All the players were 'clean.'
"When you get into the fifth or sixth hour of a match and both players are fatigued some drugs will certainly make a difference," a FIE spokesman said.