At the 1968 Summer Olympics in Mexico City, he won the 1500 metres gold medal (defeating American favourite and world record holder Jim Ryun by 20 metres, the largest winning margin in the history of the event) and 5000 m silver medal. Four years later, he won the 3000 metres steeplechase gold and 1500 metres silver at the 1972 Summer Olympics in Munich, Germany. He retired in 1973. He is on the cover of the October 1968 issue of "Track and Field News", the first issue following the Olympics. He shared the cover of the September 1969 issue with Naftali Bon.