A star center in his two years of college basketball at Jacksonville University, Gilmore led the Dolphins to the NCAA Division I championship game in 1970, where his team was beaten 80–69 by the UCLA Bruins.

Under coach Eddie Holbrook, Gilmore led Gardner-Webb to the NJCAA tournament in 1968 and 1969, playing alongside George Adams.

[11] The following season Gilmore's strong play continued, as he and Dan Issel led the Colonels to a 56–28 record and the 1973 ABA Playoffs.

Eventually, after beating the Carolina Cougars in a seven-game division finals series, Gilmore and the Colonels made it to the ABA Finals, but lost to the Indiana Pacers in another hard-fought seven-game series, despite Gilmore averaging 22.1 points, 17.3 rebounds, 5.3 assists, and 4 blocks per game.

In the final game of the series against the Indiana Pacers, Gilmore scored 28 points and grabbed 31 rebounds in front of 16,000 fans at Freedom Hall.

Four of its teams (Denver Nuggets, Indiana Pacers, New York Nets, and San Antonio Spurs) were absorbed into the NBA in the ABA–NBA merger, and the remainder, including the Kentucky Colonels, folded.

[17] On March 18, 1977, Gilmore scored an NBA-career-high 42 points, along with grabbing 15 rebounds and recording 9 assists, in a 114–112 win over the Kansas City Kings.

Gilmore was traded to the San Antonio Spurs in July 1982 for Dave Corzine, Mark Olberding, and cash considerations.

[20] There, coached by Stan Albeck, he teamed with spidery 6’8” shooting guard George “The Iceman” Gervin to provide the Spurs with a potent inside-out game.

While the Spurs would continue to make the postseason in subsequent years, they would not again advance out of the first round during Gilmore's tenure.

[23] Gilmore played the 1988–89 season with Arimo Bologna of the Italian league, where he averaged 12.3 points and 11.0 rebounds and made the European All-Star Team.

[24] At the time of his retirement in 1989, Gilmore was the NBA's career leader in field goal percentage (minimum 2,000 shots made) with 59.9%.

[5] In 2007, Gilmore took a position as Special Assistant to the President at Jacksonville University, his alma mater, serving in various public relations capacities.

[25] Gilmore provides radio color commentary for Jacksonville University on the school's flagship station, WJXL.

Gilmore was also a frequent guest on the basketball call-in show Ballin' with Al Edwards, also on WJXL.