Aileen O'Connor, 16, of College Park, representing the D.C. CYO Club, broke open a close race and captured first place while leading the CYO to a share of the team title in the second annual Eastern Regional Women's 10-kilometer championship in East Potomac Park yesterday.

O'Connor ran almost step-for-step with Charlotte Lettis, 26, of Amherst, Mass., and the Sugar Loaf Mountain Athletic Club during the first four miles of the 6 1/2-mile test.

"Then, right at Hains Point. I picked up the pace and eventually got away from her," O'Connor said. "But I was never sure I had it until I reached the finish line."

"I just couldn't go with her when she picked up the pace," Lettis admitted. "But I really enjoyed the race today because it was so close and so exciting."

O'Connor's winning time was 35 minutes 26 seconds, while Lettis turned in a 35-minute 44-second performance to pace the 345 starters.

Lettis led her team to a tie with the CYO for top honors. Other scorers for Sugar Loaf were Dia Elliman, 20, who took 10th place and Sue North, 21, who finished 12th.

Iaddition to O'Connor, the scorers for the CYO team were Jill Haworth, 16, who finished seventh, and Tita Lewis, 15, 16th.

Skip Grant, the coach of the enthusiatic CYO contingent, spoke with pride about his team after the race.

"As you can see, we've got all ages, shapes and colors on this team, but they blend together very well," Grant said.

The 42-year-old Washingtonian is a volunteer coach for the 50 boys and girls on this CYO team in addition to his duties as a salaries coach for the St. Albans cross-country team.

Third place went to Mary Shea, 16, of Raleigh, N.C., who finished in the same position in last year's race. Last year, Mary's older sister, Julie, won the race, setting a record for American women in the 10-kilometer run. Julie did not compete here yesterday.

"Julie ran for N.C. State in a cross country meet yesterday and finished first," Mary explained. "Her coach knows how hard she works in these races and he didn't want her to come up here and injured herself or anything."

Trudy Rapp, 40, of Alexandria, won the veteran's division, for runners 40 years and old.