Chris Mason, running in only his second marathon, led the final 21 miles to win the 18th annual Washington's Birthday Marathon yesterday in frigid conditions at the Beltsville Agricultural Research Center.

Mason, 30, a former middle distance runner at Villanova University, took the lead five miles into the race and finished the 26-mile 385-yard distance in 2 hours 26 minutes 41 seconds.

Fred Steier of Philadelphia, who trains with Mason, finished second, almost seven minutes behind (2:33:12).

"I'm stiff and cold," was Mason's self-evaluation after covering the marathon distance over Center roads in 10-degree temperatures.

"But I didn't notice the cold that much while running," continued the Ardmore, Pa., resident, who came over from his birthplace, Sheffield, England, to run at Villanova 12 years ago. "I was running well so I didn't notice the weather. Plus, I had covered every part of my body I could."

Mason, who is employed by the University of Pennsylvania treasurer's office, has been running long distances for one year. He said he decided to run the marathon because "I saw lesstalented people doing well running it so I decided to try."

Mason's only other marathon was November's Marine Corps event where he finished 18th, with a time 10 minutes slower than yesterday's.

Of 559 runners entered in the race, only 372 showed up. Women held 23 spots in the starting field.

Steier, running in his 12th marathon, chopped five minutes off his previous best. The 31-year-old communications teacher at Penn related some effects of the cold weather.

"It froze my lips together so that I couldn't talk. I couldn't even get any nourishment from the squeeze bottle my wife tossed me. But, other than that, I didn't mind it. It kept me from getting dehydrated."

Only 242 of the 372 starters completed the full distance.

"We were encouraging people to drop out," said Larry Noel of the D.C. Road Runners. "There were at least 15 cases of hypothermia and frostbite. The runners most of the time did not even realize they were showing the effects."

Mike Sabino of Baltimore placed 30 seconds behind Steier and Robert Stack of Rockville came in fourth with a 2:34:58 clocking. Forty-five men completed the race in under three hours and qualified for April's Boston Marathon.

The top female finisher was 17-year-old Val Hardin of Woodbridge, Va. She placed 81st with a time of 3:09:39.