3-time World Welterweight Champion and 2-time WBA Middleweight Champion; he is remembered for his fight with Benny Paret in 1962.
He worked at a hat factory as a teenager.
He was named BWAA Fighter of the Year in 1963 and Ring Magazine Fighter of the Year in 1964.
He married dancer Mercedes Donastrog in 1971. They had a son named Luis.
He lost to Vito Antuofermo on November 22, 1974.