FIFA says doping samples from World Cup players in South America are arriving at a laboratory in Switzerland within 33 hours.
FIFA and the World Anti-Doping Agency-accredited lab in Lausanne are under time pressure to test samples before a player's next match several days later.
Testing for the World Cup in Brazil is being done in Lausanne because WADA stripped the Rio de Janeiro lab's status for repeated errors.
All 736 players at the World Cup will provide pre-tournament blood and urine samples.
FIFA chief medical officer Jiri Dvorak says the first 750 samples have arrived in Switzerland "from several Latin American countries in less than 33 hours."
Dvorak says all samples arrived in good condition in cooled transit boxes.
Two players from each team are randomly chosen to give samples after each match.