PORT-AU-PRINCE, HAITI, FEB. 6 -- Five years to the day after the Duvalier dictatorship collapsed, Haiti is to install its first democratically elected president Thursday, the Rev. Jean-Bertrand Aristide.

Aristide, 37, a leftist priest who was ejected from his Roman Catholic order for preaching what his church considered to be class warfare, enjoys a near-mythic stature among Haiti's poor masses, who gave him two-thirds of the popular vote in a field of 11 candidates in December's presidential elections.

But on the eve of the country's democratic milestone, there is an undercurrent of anxiety as economists, Haitian businessmen and international aid donors size up the little that is known of Aristide's plans to run the hemisphere's poorest economy.

The doubts about Aristide's economic program reflect a wider uncertainty about how and whether Aristide can harness the overwhelming popular adulation he commands. In interviews this week, businessmen expressed fears of a higher minimum wage, centralized planning, nationalization of industries, even street rioting.

So deep is the uncertainty that imports are said to have slowed substantially as businessmen seek to reduce their inventories and empty warehouses as a precaution against looting.

A Haitian economist said some exporters are making contingency plans to move their production operations to the neighboring Dominican Republic, so they would be able to honor delivery contracts in case of disorder in Haiti. Investments have been delayed.

"If Aristide doesn't succeed we're going to be the ones who lose," said a downtown businessman. "The ones at the bottom don't have much to lose except their hope for change."

Anxiety has intensified partly because Aristide has given no hint of whom he will appoint to important positions, including the key post of prime minister. Aristide's transition team includes Marxists and moderates, and rumored candidates for prime minister run from centrist business figures to leftist politicians with radical followings.

The incoming government's diplomatic intentions have been equally obscure. Aristide and many of his backers have been hostile to the United States, accusing it of having backed previous dictatorial Duvalier governments. Some diplomats noted that Cuba is sending 26 people to the inauguration -- one of the largest official delegations.

"The whole world is in the dark" about Aristide's intentions, said one Western envoy. "Probably his own people are."

Aristide's camp has sought to calm the fears by issuing a number of vaguely reassuring statements recently, hinting that he has evolved from his days as a fiery priest. "A prophet speaks in the name of the masses. A president speaks for the whole population," he told a press conference during a visit to France last week.

One of his key political allies, Port-au-Prince Mayor Evans Paul, has given assurances to landowners that their rights to private property will be respected and that peasants who try to seize land will be evicted by the government.

But Aristide has made no recent public statements about his economic plan, leaving economists to puzzle over campaign documents for clues about how the new government will proceed. "We are working to solve Haiti's problems," said Renaud Bernadin, a top adviser to the president-elect. "We are not guided by free-market capitalism, protectionism, communism or socialism."

Haiti's economy is in dire straits, the result of decades of the Duvaliers' corruption, inefficient state industries and, since 1986, political instability that produced five governments in five years.

Per capita income is about a dollar a day. Unemployment is nearly impossible to measure, given the large number of people who work informally at odd jobs, but it is believed to be very high, perhaps above 50 percent.

The large majority of Haitians cannot read or write, and the urban slums are breeding grounds of disease, which the government cannot afford to combat with public health programs. Burdened by inefficient state-run enterprises and mismanagement at all levels, the government must print $5 million a month to cover its $60 million annual deficit on a total budget of about $240 million.

Asked what Aristide's biggest economic problem was, Leslie Delatour, a former finance minister, responded: "It's like asking me what Saddam Hussein's biggest problem is. He has so many of them -- just pick one and you can't go wrong."

It was this panorama of despair that Aristide described and reflected in the sermons that brought him a national following. His studies included theology, psychology and languages, but not economics.

If there is any unifying theme to the economic vision his campaign documents outlined, it is that the government should be the main engine of development. By implication, the private sector is given short shrift.

Aristide's advisers and campaign documents have suggested that inefficient state-owned industries, such as a flour mill and cement factory, should be protected from foreign competition by high tariffs.

In a similar fashion, they have also hinted that Haiti's farmers will be protected with tariffs and subsidized prices. But that policy seems at odds with another major theme of the incoming government -- to lower the cost of living for Haitian consumers.

Aristide has vowed to find savings and new revenues by fighting corruption and featherbedding in government. But economists say that while there is fat that can be cut, it will not provide enough new revenue to subsidize farmers or finance ambitious new government programs.

In the short term, the government will have to find nearly $9 million a month in hard currency to pay for oil imports. To cover the oil bill and a recovery program, the United Nations has drafted plans for a $400 million aid program for 1991, to include funds from international organizations as well as Haiti's traditional bilateral donors, including the United States and France.

Special correspondent J.P. Slavin contributed to this report.