It's a far cry from the days in 1975 when Beirut businessmen were fleeing their bomed-out city, arriving in Athens with briefcases bulging with cash.

Today, foreign business presence in this capital has doubled and, by the end of 1977, and estimated 300 multinational companies will have established their regional headquarters in Greece.

With new firms coming in one the average of ten per month, Athens, in the view of financial circles, is well on its way to becoming a major international business center for the Eastern Mediterranean and the Middle East.

"It began with those who relocated their Beirut headquarters," said management consultant Gordon Ball. "But the most significant trend now is an acceleration in the number of new companies setting up regional headquarters in the area for the first time," he said.

"The success of those who moved from Beirut prompted others to come to Athens. There's really no viable alternative today. Beirut is dead as a business and banking center. And, if you're doing business in Eastern Europe, Africa or the Middle East, what better place than Athens? It's on its way to becoming the Easter counterpart of Brussels . . . If the present pace continues, by 1980 there will be 500 multinationals headquartered in Greece," he added.

The list of those now operating out of Athens, including 170 American firms, reads like a "Who's Who" in business and finance: Citibank and Chase Manhattan, Boeing Goodyear, ITT, General Motors, Wilkinson Sword and International Harvester.

"The short-term benefits are terrific," said one American executive, citing the attractive tax-free status given to companies with headquaters in Athens, although they are not permitted to conduct commercial activities inside Greece.

"There are also superb communications and flight connections. Within and hour, you're in the Middle East. Schools are good and housing reasonable," he continued. "There's political stability. It's cultivated and civilized But, in the final analysis, if one's working the Middle Eastern market, one cannot escape the ultimate drawback: Greece is not and Arab state."

But there were few options available inside the Arab world to the Beirut community. Cairo's bureaucracy and communications are deplorable.Amman is too unsophisticated a town. Bahrein has set its own restrictions. Tehran is overcrowded and overpriced.

Athens, as clearly the most popular new base in the area, had little competition. Considering the vilatility of the Middle East, it was clearly to Greece's advantage that she has not given full diplomatic recognition to Israel today.

"There's still a lingering nostalgia, however," one American businessman said. "Beirut was the only place where sophisticated banking and commerce, swimming pools and the Casino de Liban, provided a lifestyle of big money and easy contacts. And doing business with the Arabs is highly personal. You just don't have the contacts in Athens, and you can't monitor the Middle East from Greece."

But so long as the momentum continues, the Greek government, eager to become a prestige capital and in critical need of foreign exchange, has attempted to make Athens even more attractive to multinational firms.

Aware of the structural weaknesses which work against Greece's becoming and international banking and financial hub, the government has adopted new legislation which radically modifies currency control for offshores financing, both banking and mercantile. It also has attempted to streamline an entrenched bureaucracy and give new flexibility to the legal framwork and to generally outdated banking and currency laws.

A touchstone of Premier Constantine Karamanlis' foreign policy is to forge a bridge between the Middle East and Europe through Athens, and to bring Greece into the European Common Markets.

The influx of foreign nationals, numbering 60,000 today, has brought an expectable outcry from Greece's opposition political parties and from the capital's leftist press.

Liberal member of Parliament Stelios Papathemelis charged in Parliament that many of the companies provided cover for intelligence agents and that the country's independence was at stake.

More universal complaints, however, have accompanied the new glitter of Athenian prestige, where chic boutiques and restaurants have sprung up to serve the foreign community, with a commensurate increase in the cost of living for the middle- and upper-middle-class Greek.

Rents have tripled in some areas, service costs are on the rise and, although the multinationals are forbidden from doing business inside the country, many Greek interests feel indirectly threatened. They resent the tax-free status, duty-free clearances, and other priviledges that are not enjoyed by Greeks.

Greek officials argue, however, that the influx is of overwhelming benefit. It has created more than 5,000 jobs and provided professional training and opportunities for managerial expertise. According to national figures, salaries paid by the multinationals are 30 to 100 per cent higher than those paid by businessmen in Greece.

During 1977, the multinationals will spend an estimated $90 million in Greece. Consultant Ball says this figure "approaches 10 per cent of total revenue from tourism, the country's Number One source of foreign exchange, without any of the infrastructure investment or general disruption that tourism inevitably brings."

"There is absolutely no question," said a government economist. "On every level, we want them to stay."