In his amateur career, Rademacher had 79 fights, going 72-7. He won a series of tournaments, including the 1949, 1951, 1952, and 1953 Seattle Golden Gloves (he lost in 1950 to Zora Folley, who he would face several times in his career), and the US Amateur Championship as a heavyweight in 1953—avenging his earlier loss to Folley. He also captured the Chicago Golden Gloves, the All-Army championship, and the Service championship in 1956, before qualifying for the Olympic team. In the Olympics, held in Melbourne, he captured a gold medal in the heavyweight division.