Erik Morales, the Mexican fighter who won world titles at four different weights, has been suspended from boxing for two years after testing positive for banned drug Clenbuterol.
He tested positive for the prohibited anabolic agent in October 2012, said the United States Anti-Doping Agency.
The 36-year-old won super-bantamweight, featherweight, super-featherweight and light-welterweight world titles.
The man nicknamed El Terrible claimed a memorable 2005 win over Manny Pacquiao.
Morales has had 61 professional fights and his 52 victories also include successes against Northern Ireland's Wayne McCullough and fellow Mexican Marco Antonio Barrera.