Gilmore followed 5 All-Star seasons with the Kentucky Colonels of the ABA by becoming the 1st overall pick of the 1976 NBA dispersal draft, which was held after the ABA was disbanded, as four teams transferred to the NBA. In Gilmore's complete pro basketball career, he was an eleven-time All-Star, the ABA Rookie of the Year, and an ABA MVP, and he remains the NBA career leader for field goal percentage.
Nicknamed "The A-Train", the 7' 2" (2.18 m) Gilmore once played in 670 consecutive games.
Gilmore was born in Chipley, Florida, and reared there and in Dothan, Alabama, a larger community 35 miles to the north. He graduated from Dothan's Carver High School in 1967. Gilmore played college basketball at the Gardner-Webb Junior College for two years and at Jacksonville University for two years, leading the Jacksonville Dolphins team to the NCAA title game in 1970, where they lost 80-69 to UCLA. During the two years that Gilmore played NCAA basketball at Jacksonville, he became one of only five college basketball players ever to average at least 20 points and 20 rebounds over his career. Gilmore led the NCAA in rebounding both years at Jacksonville, and his career average of 22.7 rebounds per game is still the highest in NCAA Division I history.
Gilmore began his professional career with the Kentucky Colonels of the American Basketball Association for the 1971-72 season, signing a record high-paying contract. He was so immediately dominant that he earned the rare distinction of being selected both the Rookie of the Year award and the league Most Valuable Player award for his first season.
Over his five-year ABA career, Gilmore led the ABA four times in rebounding average, twice in both field goal percentage and blocks per game, and once in personal fouls. He was named to the All-ABA First team five straight seasons, and the All-Defense team four times. He played in the ABA All-Star Game all five years he was in the league, earning the 1974 game's MVP. The capstone of his time in the ABA was leading the 1974-75 Kentucky Colonels to the 1975 ABA championship and being named the ABA Playoffs Most Valuable Player.
During his days as an ABA dominator, Gilmore established league records for career blocked shots (750), blocked shots in a season (422 in the 1971-72 season), and rebounds in a game (40).
The ABA ended its existence after the 1976 season, with four of its teams (Denver Nuggets, Indiana Pacers, New York Nets, and San Antonio Spurs) joining the NBA in the ABA-NBA merger, and the remaining teams, including the Kentucky Colonels, folding. Since his team, the Kentucky Colonels, had folded, Gilmore went into the special 1976 ABA dispersal draft, and he was chosen with the first overall pick by the Chicago Bulls. While not the same force that he had been in the ABA, after four All-Star selections in five solid basketball seasons in Chicago, Gilmore was traded to the San Antonio Spurs in 1982. Twice again an All-Star in San Antonio through 1987, he rejoined the Bulls for part of the 1988 season before finishing his NBA career with the Boston Celtics in 1988.
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.
Gilmore played in a total of six NBA All-Star Games. He led the NBA in field goal percentage in four consecutive seasons, including a career best 67% during the 1980-81 season — the fifth highest percentage in NBA history. He remains the NBA's career leader in field goal percentage (minimum 2,000 shots made) with 59.9%.
Following his playing career, Gilmore has been active in the Jacksonville community.
In 2007, Gilmore took a position as Special Assistant to the President at his alma mater, serving in various public relations capacities.
Gilmore also provides radio color commentary for his alma mater 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.