TOKYO, SEPT. 17 -- If the International Olympic Committee has a sentimental bone in its collective body, the ancient city of Athens should win in a walk Tuesday when the members choose the site of the 1996 Summer Games.

But in an era of broadcast contracts worth megabucks, mammoth national teams, and mushrooming security and environmental worries, will sentiment be enough to win the day?

That's the question nobody could answer here today as the 87 current members of the Games' governing board met in a sprawling hotel complex. Tuesday they will vote among Athens and five other cities contending for the Olympiad that will mark the 100th birthday of the modern revival of the ancient Greek athletic competition.

"This choice is so up in the air that nobody, on the committee or off, can predict who will win," said Robert Helmick, the Des Moines lawyer who has one of the two U.S. votes on the committee as president of the U.S. Olympic Committee. Anita DeFrantz, a former Olympic rower and president of the Amateur Athletic Foundation, has the other.

The six contending cities -- Athens, Atlanta, Belgrade, Manchester, England, Melbourne, Australia and Toronto -- each will make a half-hour presentation to the committee Tuesday, and Helmick said that could be unusually important this time.

"It's like a jury trial," he explained. "In a close case, the summation can be decisive."

Following these final plugs, the vote will be taken in a series of secret ballots. The sealed envelope containing the name of the winning city will be opened, Oscar-style, by IOC President Juan Antonio Samaranch.

With Samaranch not voting, the winner needs its name on 44 ballots. The low city drops out in each round until the winner is chosen, and the results of each round are posted before the next round.

Although nobody here was predicting a winner, there is a strong emotional pull on the committee toward Athens, largely for historical reasons.

The first Olympic Games -- probably a series of running, chariot, spear, and archery competitions among Athenian soldiers -- were held near the base of Mount Olympus in Greece during the 8th century B.C. The signature event of the modern Olympics, the marathon, is based on a famous moment in Greek history, when the Athenian Army messenger Phidippides ran 26 miles 385 yards and then, with his dying breath, gasped out the words "Victory at Marathon!"

When the French nobleman Baron de Coubertin convinced the world to revive the Olympic tradition in 1896, he held the first Olympiad in Athens, and the marathon race traced Phidippides' steps.

All that history would be relived, of course, if the centenary of de Coubertin's Olympic dream were scheduled for Athens.

In addition to history, Athens has excellent athletic facilities that clearly have impressed committee members, Helmick said. But Athens also has major traffic bottlenecks and a pollution problem so severe that the ancient Greek temples are corroding. If air pollution in Greece is so bad it can imperil the Parthenon, what will it do to an athlete's lungs?

Athens, Belgrade, and Manchester all face a geographic problem as well. Since winter and summer Olympics will be held in Europe in 1992 (Albertville, France, and Barcelona), the committee may want to move to a different continent for the '96 Games.

Atlanta and Toronto have a somewhat similar problem because Olympiads were held in their countries -- Los Angeles (1984) and Calgary (1988) -- within the decade. Melbourne's boosters have been pushing this geographic argument hard, noting that no Olympics has been held in the Southern Hemisphere since 1956 -- in Melbourne.

The Atlanta contingent here, which includes Mayor Maynard Jackson and former congressman and mayor Andrew Young, has been talking up both the city's old-fashioned charm and its up-to-date broadcast facilities. Among other things, Atlanta has promised customized television feeds of the '96 Games all over the world.

Amid the low-key campaigning of the six cities, the IOC acted on a few other issues. The members decided today to continue the ban against South African participation in the Olympics but left open the possibility that the political changes there could prompt a reversal.

The IOC said it was joining with five national mints to produce a series of legal coins carrying the Olympic rings as part of its 100th birthday celebrations. The coin program will involve Austria, Australia, Canada, France and Greece, each issuing one gold and two silver coins in succession from 1992 to 1996. Each will have its own theme. The U.S. Mint was approached about joining the coin program but a difficult legislative process ruled out American involvement.

The committee also voted to continue the practice of releasing a flock of doves (actually, white pigeons are normally used) during Olympic opening ceremonies. Some pigeons evidently were roasted by the Olympic flame on opening day of the Seoul Olympics in 1988, and that prompted animal rights groups to demand a change for future Olympiads.