Liquori made the U.S. Olympic team in 1968 as a nineteen-year-old freshman. He reached the finals of the 1,500 meter run but suffered a stress fracture and finished 12th. He was the youngest person ever to compete in the final.
In 1969, he finished second to Ryun in the NCAA indoor mile, then won the NCAA and AAU outdoor mile championships by turning the tables on Ryun and beating him. He repeated the AAU outdoor in 1970 and had his best year in 1971, winning the NCAA and AAU outdoor titles, and a gold medal in the 1,500 m at the Pan-American Games. In 1969 and 1971 he was ranked number 1 in the world for 1500 meters/mile. In 1977 he was ranked number 1 in 5000 meters and set a U.S. record of 13:15.1 while finishing second to Miruts Yifter in the inaugural World Cup.
On May 16, 1971, Liquori lowered his personal best to 3:54.6 in the Dream Mile in Philadelphia and beat Ryun by a few steps.
But Liquori was injured later that year. He didn't return to competition until 1973. In 1975 he ran a personal best 3:52.2 in the mile, finishing second to Filbert Bayi (who broke Ryun's world record in that race by 0.1 second with a 3:51.0), and set a United States record of 8:17.12 in the 2 mile. Liquori retired from competitive distance running in 1980.
He has written an autobiography, On The Run, and he also wrote Guide to the Elite Runner and Home Gym Workout. He was a founder of The Athlete Attic Footwear chain in 1971.
Liquori lives in Gainesville, Florida. He does commentary for NBC at the Olympics and at various track and triathlon events around the country. Liquori was diagnosed with chronic lymphocytic leukemia (CLL), which is now in remission. He picked up the guitar after a 35-year hiatus and is currently a professional jazz guitarist and now performs Monday and Thursday nights with various ensembles at Leonardo's 706, a self-promoting Gainesville restaurant.