A succession of international crises--from the Iranian revolution to Latin American debt -- has caused an explosive growth in the political-risk-insurance market, as U.S. companies increasingly seek to protect their overseas investments from political and economic upheavals, according to government and private-sector analysts.

The Overseas Private Investment Corp. (OPIC), a quasi-governmental agency that insures U.S. companies against economic losses caused by Third World turmoil, recently reported that it has nearly tripled its volume over the past three years, writing a record $4.3 billion worth of insurance policies on 123 projects in the fiscal year ending Sept. 30.

The most popular of OPIC's policies was "war, revolution and insurrection" coverage, which recently was broadened to include insurance against "civil strife," such as acts of political terrorism and sabotage.

In addition, some private insurance companies have moved aggressively into the market by feeding on corporate anxiety over expropriations and foreign exchange shortages caused by the debt problem. AIG International, which has a political-risk department that writes policies against such contingencies, has enjoyed a 30-percent-per-year growth in this area for the last four or five years, according to a company official.

Another large private competitor, Cigna Corp., says that it will collect $22 million in political risk premiums in 1984 alone -- three times what it collected the year before.

"Political-risk insurance has mushroomed into something that all major companies look into before investing abroad," said Marjorie Rawls Roberts, an international trade lawyer who specializes in this kind of insurance. "It's very much of a growth field."

In fact, in some overseas markets, such as the Middle East, American companies may have no choice: Roberts said that banks increasingly are pressuring their customers to take out such insurance policies before approving loans for overseas projects. "It's definitely a factor in deciding whether to make a loan for a particular investment," she said.

At the same time, however, the risk boom also is increasing the costs of doing business abroad. OPIC's maximum coverage (a package that includes "war" coverage as well as separate policies covering expropriation of assets and inconvertibility of funds) will cost a company annual premiums amounting to 1.65 percent of its insured investment. Thus, a typical company that has taken out a 20-year policy on a $20 million overseas plant, will end up paying annual premiums of $330,000, or $6.6 million over the life of its policy.

The surge in business has been most evident at OPIC, a small agency that until recently was "Washington's best-kept secret," according to its president, Craig A. Nalen. Created in 1967, the agency offers insurance and loans for investing in developing countries with per capita incomes of no more than $2,952 (although the agency's board is empowered to make exceptions for projects it deems worthy -- the reason OPIC has offered hundreds of millions of dollars worth of insurance in Saudia Arabia and Israel).

In its early years, OPIC frequently was attacked by liberals in Congress, led by the late Sen. Frank Church, the Idaho Democrat who accused it of subsidizing multinational corporations and increasing the likelihood of U.S. meddling in the Third World. A General Accounting Office study in 1977 found that 41 percent of OPIC's insurance went to 11 big multinationals and 29 percent went to just three of them, Dow Chemical Co., W. R. Grace & Co. and J. P. Morgan & Co. Inc.

Today, OPIC officials insist that they have corrected the problem, largely through a dramatic increase in business that has broadened their customer base. Although such multinational giants as Chase Manhattan Bank, General Electric Co. and Tenneco Inc. still dominate its client list, OPIC says that more than 33 percent of all its sponsored projects now go to small businesses, defined as any company with annual gross sales of $120 million or less.

"We've written more insurance in the past four years than we did in the previous 10," said Robert Jordan, OPIC's director of public affairs.

Profits earned from these transactions also largely have helped OPIC to slay the "government subsidy" charge. OPIC had enough excess reserves to present the U.S. Treasury with checks for $50 million in 1981 and $56 million in 1982, thereby repaying its original $106 million endowment from the government.

What has caused the boom? To a large extent, OPIC can thank the Ayatollah Khomeini, whose Islamic revolution devastated U.S. companies' investments in Iran. Despite the warnings of some political seers that the shah's regime was shaky, most U.S. companies stuck by the conventional wisdom and failed to insure themselves against unpleasant political contigencies, according to Felton McL. Johnston, vice president of OPIC's insurance department.

"A lot of companies got burned in Iran," Johnston said. "A lot of people really felt they had good connections in the country, and those connections didn't survive the revolution. They had made an assessment that there might be political turbulence but the basic structure would hold."

One company that suffered from that miscalculation was American Telephone & Telegraph Co., whose foreign division, then called American Bell International Inc., had a major $50 contract to modernize and upgrade Iran's telephone system, only to have its $50 million performance bond called by the government's new rulers after the shah's regime was toppled. These days, AT&T is not nearly so confident. Last year, American Bell's successor, AT&T International, took out four separate insurance policies with OPIC totaling nearly $60 million to protect similar telecommunications contracts in Egypt, Saudia Arabia and South Korea.

"This is akin to purchasing insurance on your automobile," said John P. Mattern, AT&T International vice president. "It's the kind of thing that any prudent person would do."

Yet there is more than just prudence to the recent surge in companies buying one brand of political-risk insurance -- inconvertibility coverage, which protects against foreign exchange shortages that frequently result in U.S. firms being unable to convert their foreign currencies into dollars. The popularity of these policies -- which are offered by OPIC and the private sector -- has grown enormously since the debt problem first struck U.S. investments in Mexico in 1982, risk experts say.

Some add that one good example of this is Citicorp, which recently disclosed that it had taken out a $900 million policy with Cigna to insure itself against "prolonged delays" in receiving payments on its loans to such financially troubled countries as Brazil, Argentina, Venezuela, the Philippines and Mexico.

The Citicorp policy does not apply to outright defaults or debt repudiation, but it does cover convertibility problems: If a Citicorp debtor has the local currency to pay off its loans, but can't obtain the dollars it needs from its central bank, Cigna would cover Citicorp's losses.

Joseph Tunney, a vice president of Chemical Bank who also serves as the president of the 300-member Association of Political Risk Analysts, cites such policies to support his contention that "there is probably more uncertainty than there's ever been" over foreign investments.

But officials at OPIC say that, at least for their part, the political-risk boom has at least as much to do with their own more aggressive marketing efforts as heightened uncertainty throughout the world. Nalen, a Florida businessman whose varied career included ownership of a land development company and a stint as chairman and president of STP Corp., ordered a market research survey shortly after he arrived in 1981 and found to his chagrin that "less than 5 percent of U.S. companies had ever heard of OPIC, much less being familiar with its programs."

As a result, OPIC launched an aggressive $2-million-a-year marketing program, complete with direct mailings, teleconferencing and large advertisements in such publications as Business Week, Fortune and The Wall Street Journal.

Given the nature of their product, OPIC's ads make their point somewhat gingerly. Instead of scary pictures of religious fanatics, leftist guerillas and Third World riots, OPIC ads used what public affairs director Jordan calls the "soft sell": enticing photos of exotic foreign locations accompanied by tag lines promoting the virtues of foreign investment.

"We don't want to give everybody the impression you're going into the jaws of hell when you're going into these places," Jordan said.