Gilliam continued his college basketball career with UNLV. Gilliam played for UNLV from 1984 to 1987 and was an integral part of a team that was 93-11 in the three years he played for the Rebels. The UNLV team was ranked number one in the country for most of the three years Gilliam competed and the team made it to the NCAA tournament every year during his stay. In 1987, the team reached the Final Four and Gilliam was named to the NCAA Final Four all-tournament team. Gilliam scored 998 points in his senior year, which remains a school record for the most points scored in a season by a UNLV player. Gilliam also played on the UNLV team that won 38 games in a season, which is still an NCAA Division 1 record for most wins in a season. In 1987, Gilliam was selected for a number of All-American Teams and voted the top contender for the John Wooden award. While at UNLV, teammate Frank James gave him the nickname "The Hammer" after seeing Gilliam's biceps combined with his pounding action under the basket. Gilliam said, "He knew I was from a steel town, too. I think that was a factor." The "Los Angeles Times" dismissed the notion that he got the name from a baking powder, Arm & Hammer.