Last October, 80 U.S. businessmen flew to Istanbul for three days at their own expense to meet the people who run Turkey. They sat through seminars and speeches, but mostly talked informally with government ministers, businessmen, bankers and politicians.

In February, several prominent Turkish businessmen came here for three days of meetings with U.S. industrialists, bankers and officials at the American Friends of Turkey, a Washington-based private association. Assistant Defense Secretary Richard N. Perle and Assistant Secretary of State Richard R. Burt were among the welcoming speakers. A similar session was held in New York early last month.

The United States is the world's biggest credit market. To poor countries, hundreds of banks here appear swamped with money seeking high-interest rates, and the capital-starved countries are willing to deal. Commercial arrangements are more quickly and easily financed here than almost anywhere in the world, and foreign diplomats spend much of their time wooing bankers and businessmen.

U.S. businessmen offer another perk: the protective interest of the U.S. government.

"If you get American business involved in and interested in Turkey, they will influence the opinion makers in this country," said Army Col. Ralph Ropp, who founded American Friends of Turkey after being stationed there. That, he said, will further all of Turkey's other political goals.

"We want to be the supermarket of the Middle East," Ali Kocman, president of the Turkish Businessmen and Industrialists Association, told the February gathering. "We're going to sell frozen chickens . . . , and that means we need chicken feed, fences, roads and refrigerated trucks. American businessmen should take a good hard look at Turkey for joint ventures."

To most developing nations, the magic phrase that will open the gates to prosperity is "joint venture." With U.S. bank loans, U.S. firms provide the plant and teach the know-how in return for a share of the profits for a limited period. When they leave, the plant stays, along with its jobs and profits.

In an effort to work this magic, each country does an elaborate courtship dance before the pin-striped financiers, most of whom are nervous. Turkey's track record, like that of many other countries competing for investors' favor, is not reassuring.

A U.S. fertilizer company executive had spent months trying to collect a $2.5 million debt from the Turkish government in 1976, and finally cornered the president of the Central Bank of Turkey in his Ankara office. The banker, fidgeting and evading every suggestion of a payment schedule, suddenly jumped up, strode to the window and waved toward the crowded boulevard below.

"Look!" he cried. "That's how you'll be repaid: by the dynamism of the Turkish people!"

The former executive laughed as he told the story, and then added, "But you know, in fact that's how it worked."

Turks are just beginning to want the stuff and nonsense of consumer living. In a tradition common in many eastern nations, village women have always used extra money to buy gold bracelets instead of more basic consumer goods, wearing them from wrist to elbow if possible, although many live in dirt-floored shacks.

This practice keeps the family money safe from shaky banks and governments, but for a cash-starved nation the bangles are an economic black hole. About $20 billion is locked out of the Turkish economy on the arms of its women, estimated Tarhan Danisman, director of the Turkish Akbank's U.S. branch.

He assures prospective investors that the tools of rampant capitalism are prying loose the gold. Savings accounts are offering temptingly high interest, schooling is improving. As more Turks work and vacation out of the country, they are learning to covet cars, television sets and vacuum cleaners.

But there are other obstacles. As has happened in many highly nationalistic countries, Turkish laws traditionally have been hostile to foreign enterprises. When Kemal Ataturk founded the modern state on the wreckage of the Ottoman Empire after World War I, he walled off his infant economy from import competition. He spurned foreign investment as subversive to the goal of self-sufficiency.

As a result, U.S. and European business never got a real foothold in Turkey, in contrast to their influential roles in Latin America and other former colonial areas. The state-run companies grew bloated and inefficient, choked by a bureaucracy set up to provide not services but jobs.

The Turkish business style also retains much of the bazaar, common to many less-developed nations: a deal is still a highly informal, lengthy and personal process.

U.S. businessmen routinely offend prospective partners by insisting on talking business in the car leaving the airport. Turks accustomed to dealing on a handshake "don't really grasp the western legal system, the need to tie everything down in a contract to the nth degree," said Aydin Caginalp, a Manhattan lawyer who works for firms crossing Turkish-American frontiers.

The Turks, he said, "were sitting ducks at first" for U.S. importers who sold the Turks' goods here and vanished without paying. Americans often gave up on long negotiations that the Turks thought were just becoming serious.

Turkish unions, all 930 of them, are traditionally restive and centers of resistance to perennial government wage clampdowns. None of this makes U.S. businessmen happy.

But all of that is changing, Turks tell their western prospects at every opportunity. Like other countries rescued from the brink of financial collapse, Turkey rewrote its tax and investment laws in 1980 to entice foreign money. The new military regime came down hard on the unions, arresting major leaders and outlawing political activity. Journalists and politicians who protested were jailed. Things quieted.

The Turks, following the example of other nations, hired expert capitalist advice. The investment bank trio of S.G. Warburg & Co. Ltd. of London, Kuhn Loeb Lehman Brothers International and Lazard Freres of Paris and New York is writing promotional literature to bring in foreign investment in oil and gas, mining, energy and tourism.

Other banks advise Turkey on financial decisions and help negotiate loan packages. Morgan Stanley & Co. of New York recently put together a consortium of banks that is to offer Turkey medium-term loans.

The Turkish Embassy plays a key role at the center of a network of Turkish-American bankers, lawyers, economists and merchants in New York and Washington, putting any interested businessman quickly in touch with the right people.

"It's easy to get into the loop," Caginalp said. "If people want to find me, they eventually do."

The World Bank sends 100 missions a year to Turkey, which with $4 billion in loans and 77 bank projects over the years is the fifth largest borrower since the bank was formed in 1946, according to James Chaffey, chief of the bank's Greece/Turkey division.

"We're constantly involved in making recommendations on how their institutions might work better," he said.

One two-week mission in March involved two economists checking public-investment levels and export incentives in Turkish law, two senior advisers from the World Bank hierarchy who advise the bank on policy, two loan officers who decide on specific projects, an agricultural economist and an industrial economist, Chaffey said.

Current projects include a lot of energy development plus "structural adjustment loans" helping Turkey to prod its bureaucracy, juggle its tax structure and rewrite its laws.

U.S. consulting firms are finding that they can make money putting Turkish and U.S. businessmen together, and that move into the consciousness of international financiers is a major step for any budding economy.

Turkish clothing made a hit at New York fairs in March and last month, and Macy's department store is negotiating an estimated $100 million deal to bring Turkish textiles to America in bulk. Conagra of Omaha, a food-processing company, had "useful talks" with the Turks this spring about developing frozen chickens, an embassy official said.

In the biggest shift of all, one common to developing nations finding their economic bearings, Turkey is looking away from its traditional markets and products. For the first time, it is looking to the Arab world.

Turkey's cheap food and labor threaten some European producers, and traditional markets there are static or closing.

"But the Arabs will buy anything from us because we are also Moslems," a Turkish economist said, "and they can pay in oil."

No longer very welcome in West Germany, an estimated 150,000 Turkish workers have spread through the Mideast, where Turkish construction firms are delivering on an estimated $15 billion in contracts. Turks are building dams in Nigeria and shopping centers in Riyadh, and they sent home $2.5 billion from Moslem nations in 1982, according to embassy figures.

While there, they talk of home, and 25,000 U.S. workers in Arab oil fields have become potential tourists for Turkey as a result, according to Kamil Muren, head of Turkey's tourism office in New York.

"The East is the natural market for us, but we had to discover it, and it took a long time," embassy economic counselor Nabi Sensoy said. With American business helping, he said, "we will promote an export drive there that will be beneficial to everybody."

For the first time, Turkey shows characteristics of a developed country: some shop workers are taking vacations, and working-class people occasionally change jobs.

While the situation under looser union and political controls expected after elections in November is unpredictable, a life of unending labor at the task of one's parents, with no prospect of change, is no longer the only option for most villagers.

All of this, Sensoy said, means "we've graduated, we don't need as much help as an LDC," or less-developed country, the tactful term for very poor nations. But Turkey remains among the majority of nations in that it must be very careful for a long time to come, weighing every diplomatic decision for its financial consequences.