Ed Murray, who works at St. Elizabeth's Hospital as a business manager, is an engaging, warm-hearted fellow. But right now, some 8,000 people may be directing hard feelings toward him. As the race director of the Cherry Blossom 10-miler, to be held this year on March 31 at Hains Point, Murray decided to allow "only" 4,000 runners in the field.

He said recently that 12,122 applied.

Rejection slips are in the mail now, with the acceptances having gone out earlier. Murray knows that runners take these rejections hard, but he insists that his obligation is to stage a race, not a mob run.

"A field of 4,000 is already straining it," he said. "Our course just won't handle any more. Safety is one factor. The enjoyment of running is another. We want to have a race that means as much for the person that finishes in 90 minutes as for the one who streaks in under 50 minutes. When you get 10,000 or 12,000 runners on a tight course over 10 miles, you just can't do it."

Murray is but one of many race directors who are having to limit their fields. Not too long ago, the problem was how to get more people to turn out for running events. Now the great concern is how to turn entrants away. Size limitation has become as bedeviling a problem as course logistics, adequate water stations, fast-moving finishing chutes and getting newspaper coverage.

Entry forms for many races now routinely state that only the first 3,000 -- or 5,000 or 12,000 -- applicants will be accepted. The Bethesda Chase today, sponsored by Montgomery County Department of Recreation (1401 Dennis Ave., Silver Spring 20902), is accepting only 2,000 entrants. The next New York marathon is taking 15,000. The field at Boston last April -- about 12,000 including "bandits" -- became so cumbersome that new time limitations were imposed for this year's event.

Will Cloney, the urbane and even-tempered director of the Boston marathon, said that ideally he would like no more than 1,500 in his race. "But we'll never get back to that," he said wistfully. "We're hoping now, with our new qualification, for about 6,000 in April. It's not that we're trying to keep people out but that we have an obligation to safeguard those we let in. At the end of our race, all we have is the basement of the Prudential Building. It's only so big. If we had an open meadow, as they do in New York at Central Park, it might be different. I sympathize with the idea of welcoming all comers. But we just don't have the room. Last April, when it was cold and rainy before the race, the Hopkinton gym was packed to capacity."

Frew Lebow, urbane but still working on becoming even-tempered, is the race director for the New York marathon. He is alarmed by the immense turnouts in New York. "The glamor of the Marathon has been overdone," he argued. "Too many are going into it now without ever having run shorter races. Yet these are enjoyable, too, and offer a fine challenge. I ask sponsors, 'Why don't you put up money for some 20-mile races?' They say no. They want the marathon."

New York was such a logistical success last October that Lebow and his coworkers at the New York Road Runners Club will be increasing this year's entry from 12,000 to 15,000. Talk is spreading, too, that with no Olympics in Moscow, a $150,000 purse will enhance the New York marathon.

Race directors, who are one of the earth's least-appreciated but most essential species, are entirely correct in setting quotas for their events. They realize the hollowness of the big numbers boast. Quantity can only harm quality. A competitor in a crowded race last year along the C&O Canal in Maryland was sent sprawling into the water. Luckily, he was a swimmer and made it to the bank. He lost about 30 seconds in the mishap, which reportedly was deducted from his official time.

The most obvious threats to safety come at the start of the race, when being trampled creates a hazard for everyone but the last over the line. Another danger is that the water stations will run dry.

If a tapering off occurs in the next few years, my guess is that it will be due to runners who want the simplicity of small-field races. I have been noticing this already. A friend who ran in New York in 1977 and 1978 passed it up last year for a marathon in "a Mid-Atlantic state." He declined to get more specific than that, "because you'll put the name of the race in the newspapers and the crowds will be out next year!"

Smallness has been part of the charm of the Beltsville George Washington's Birthday marathon. Its field is limited to 450, which is about the right size for the three-loop course.

As other runners begin to find that small is beautiful, one option is the ultra-marathon. The week before the New York marathon last fall, Dannon sponsored a 36-miler in Washington. About 140 runners showed up. One of them described the race as a friendly gathering of people who delighted in the communal feeling of the event. He said that was how it was in the B.C. era of running, which depending on your religion means either Before the Craze or Before the Chaos.

The message from the race directors is clear: if we want to have running room, we must make room for running. This means going to races other than the glamorous ones, in a variety of distances, and perhaps by discovering the joys of volunteering to help put on the race rather than running in it.

That's what happened last year to a fellow who came to Ed Murray's house one evening unhappy because his entry was rejected. After realizing that his anger was a case of overheating he called back to ask if he could help Murray in some way on race day. His offer was accepted. He was assigned to work the chutes.

Although this runner didn't cover a yard that day, it was one of his most memorable experiences in running. A personal best, in fact.