MILAN -- Lance Armstrong pulled out of Saturday's Milan-San Remo race, citing acute gastroenteritis.
Team RadioShack said the seven-time Tour de France champion would be replaced by Fumiyuki Beppu.
"It would not be very intelligent to let him start in a race of almost [200 miles] while not being healthy," team director Johan Bruyneel said in a statement Friday.
The Milan-San Remo is the opening single-day classic of the cycling season, and at 185 miles is one of the longest of the year.
Armstrong finished 125th in San Remo last year in one of his first races back from three years in retirement. Before retiring in 2005, he raced the Milan-San Remo six times and never won.
Armstrong is set to face rival and former teammate Alberto Contador next week at the Criterium International in Corsica.
Armstrong also is scheduled to ride in next month's Circuit de la Sarthe in France as part of his preparation for the Tour de France. It will be his fourth appearance in the race, which will take place April 6-9.
Armstrong rode the Circuit de la Sarthe in 1999, 2001 and 2003, winning a stage three months before his first Tour win in 1999.