Italy's Francesco Casagrande and Carlos Golbano of Spain were declared unfit to ride in the Tour of Spain following pre-race blood tests.
Casagrande is one of two cyclists forced to miss out
All 198 riders took the tests before the three-week race, which starts in Leon on Saturday.
"They will have to undergo another test within 15 days," said race organisers. "If they pass it they will regain their licences and be able to compete again."
The tests are to show blood levels of hematocrit and haemoglobin.
The new testing procedures were introduced by the International Cycling Union earlier this year, and have already resulted in cyclists being prevented from taking in the Giro d'Italia and Tour de France.
Lampre team leader Casagrande was banned for nine months in 1999 for high levels of testosterone but went on to win the Tour of Switzerland and come second in the Giro d'Italia upon his return to action.
Golbano rides for Spanish-based team Costa de