Charlie Cvrk of Alexandria outlasted a final effort by Jeff Peterson of Burke in yesterday's steamy weather to win the Diet Pepsi 10-kilometer road race on the Mall. A total of 4,500 runners ran the area's largest 10K race of the year.

Cvrk, 29, a Marine Corps supply system analyst, completed the 6.2-mile course in 30 minutes 7 seconds. Peterson, 27, winner of the 1978 race, finished a close second in 30:10.

Richard Shwartz of Washington was third in 31:04.

Cynthia Lorenzoni of Charlottesville took the lead for good after 1 1/2 miles and won the women's division handily in 35:49. Colleen Desmond of Fairfax placed second in 36:54.

After five kilometers in 14:44, it became a two-man race. Peterson moved alongside Cvrk as they climbed Pennsylvania Avenue toward the Capitol. Cvrk maintained his steady, relaxed stride, while Peterson worked hard to shadow Cvrk.

Cvrk surged to a five-yard lead as he rounded the corner of Constitution Avenue and 5th Street SE and passed five miles in 24:13. He extended the lead to as much as 20 yards, pulling steadily away.

Yet the race was anything but over. Charging down the hill beside the Capitol on Independence Avenue, Peterson drew within five yards with half a mile remaining.

Said Peterson, a George Mason senior who runs for the Brooks Racing Team: "He went down the hill real slow. I just coasted down the hill and right on top of him. Then he surged again on the last corner."

Cvrk sped around the final turn and 50 yards later, broke the tape, three seconds ahead of Peterson.

There were six heat-related problems treated on the course or at the finish line; one unidentified runner was hospitalized with heat exhaustion. A shortage of water at two and four miles caused problems.

Chris Brazda, race director, said officials had expected 3,500 runners, but a race day entry of 600 brought the number nearer 4,500.