Burruni successfully defended his crown by knocking out Australian Rocky Gatellari, but on 14 June 1966 he lost the championship to Walter McGowan, of Scotland, whom he had defeated previously. By this time the WBA had 'stripped' him of his title for failing to meet the organization's Number One contender, Horacio Accavallo of Argentina.
Unable to make the weight any longer, Burruni moved up to the bantamweight division. He captured the European bantamweight title by taking a 15 round decsiion from champion Mimoum Ben Ali in 1968. His attempt to secure a world bantamweight title shot ended when he was knocked out by all time great Ruben Olivares.
Burruni retired with the outstanding record of 99 wins (32 KOs), 9 losses and 1 draw.