Catholic University, leading by 15 points at halftime, survived a torrid second-half shooting stretch by Harvard and held on for a 75-68 victory last night at Brookland Gym. It was the Cardinals' second victory of the season, both at home.

Cardinal guards Joe Colletta (26 points) and Geoff Mack (23) points combined for 49 points, each on nine-for-14 shooting. They scored 29 in the opening half by working for close-in shots and rebounding furiously, while holding Harvard shooters Joe Carrabino and Don Fleming to a total of six points in the opening 20 minutes.

Catholic (2-4) shot 58 percent and held Harvard to 46. Cardinal Center Dan Murray hit five of six shots and blocked three Crimson attempts.

The second half, however, was a completely different game.

Carrabino, a 6-foot-7 forward, hit nine of 10 shots in the second half and wound up with a team-leading 23 points after scoring only four the first half. His jumpers forced Cardinal Coach Jack Kvancz to abandon his zone defense, which Carrabino was destroying from long range, for a man to man.

Carrabino's deft shooting almost singlehandedly cut the Cardinal lead from 18, near the beginning of the second half, to 63-61 with less than four minutes to play. At one stage the Crimson made seven straight long jump shots.

Then, Kvancz called a timeout to admonish Colletta for poor defense. "You have to play defense before Carrabino gets the ball," the coach screamed. "I was glad he stayed on me," Colletta said afterward. "I just had to buckle down and concentrate."

Carrabino missed his next jump shot and the Crimson were forced to foul the Cardinals in the last two minutes in an attempt to regain possession. Mack, a scholarship baseball player, hit four free throws down the stretch, as did Colletta, to secure the Cardinal victory.

"You live and die by the foul shots," Kvancz said. "We shot well in the first half. Murray was unconscious during one stretch."

"I would like to think we took care of Fleming with our defense," Kvancz said. "He may have taken himself out of the flow of their offense, but whatever, he's a bonafide player who played poorly tonight."