Throughout the late 1960s and early 1970s Czechoslovak cyclist Jiří Mainuš competed in road races all across Europe. Mainuš had a strong start to his career when he won a stage of the Tour de Pologne in 1967, before winning a stage of the Milk Race in England in 1970. That same year the quartet of Mainuš, František Řezáč, Milan Puzrla, and Petr Matoušek won silver in the team time trial at the UCI Road World Championships, which were also held in England. After riding in the Peace Race the following year, Mainuš was selected to compete in the team time trial at the 1972 München Olympics, with the Czechoslovak team finishing 13th. Back home he became a two-time national champion in the individual time trial, winning the title in 1972 and 1973. Mainuš later emigrated to the United States, where he worked as a cycling coach.