[2] Born in Houston, Texas, Renfro moved with his family to Portland, Oregon, and he attended its Jefferson High School, starring as a two-way football player and track and field athlete.

The Democrats' 1958 team is regarded as one of the greatest in Oregon prep history, which had a backfield that included him at halfback, quarterback Terry Baker (1962 Heisman Trophy winner at Oregon State), halfback Mickey Hergert (one of the leading ground gainers in the nation at Lewis & Clark College) and his brother Raye Renfro at fullback (in 1958 he broke a Portland Interscholastic League record with 24 touchdowns).

After Baker graduated, Renfro saw playing time at quarterback as a senior in 1959 and was also an all-state selection at running back, as Jefferson pursued a third consecutive title.

[4] He was named outstanding athlete in the Golden West Invitational track meet, which brought annually the nation's top high school seniors.

In 1960, Renfro enrolled at the University of Oregon in Eugene, where he excelled for the track team and as a two-way football player, an All-American halfback and defensive back.

In 1962, Renfro contributed to the university's first NCAA team championship by finishing second behind teammate Jerry Tarr in the 120-yard (110 m) high hurdles with a 13.8 time and third in the long jump with a 25'-11¼" (7.905 m) leap.

[10] That year, Renfro was part of a world-record-setting 440-yard relay team with a time of 40.0 seconds; his running mates were Tarr, Mike Gaechter and Harry Jerome.

[12] Although Renfro had won many accolades as a running back and at the time, teams put their best athletes on the offensive side of the ball, Tom Landry, looking to build a dominating defense, decided to start him at safety.

He was injured in the opening game against the New York Giants and replaced by Dan Reeves, who was so impressive that Renfro was moved back to defense when he returned to action and would end up being named to the All-Pro team again.

In the 1970 NFC Championship Game, Renfro had a key interception that led to the Cowboys' game-winning touchdown over the San Francisco 49ers that helped them get to Super Bowl V, where they lost to the Baltimore Colts, 16–13.

[2] During his time with the Cowboys, even though one of his teammates was former Olympic gold medalist and one-time world's fastest man Bob Hayes, many experts still considered him the best athlete on the team.

In 1984, Renfro coached the defensive secondary under John Hadl with the Los Angeles Express of the United States Football League (USFL).