The question is heartless but must be answered: who will profit from rebuilding Iraq?

If there's to be any hope of stabilizing the Middle East, someone has to restore Iraq's infrastructure, already hurt by than a decade of relative isolation and vulnerable to further damage in the coming conflict. And when there's work to be done, someone is going to make a lot of money from it. The numbers being discussed are enormous: $30 billion to 100 billion, according to one study from the United Nations Development Programme.

But that doesn't mean Iraq will be a goldmine for investors.

Many companies will take part in the physical rehabilitation of Iraq, but not many firms qualify for the largest deals, which, at least in the beginning, are likely to be those administered by the United States Agency for International Development. USAID bid out eight contracts tied to Iraqi reconstruction; one, a "personnel support" deal for $7.1 million, has already been won by a non-profit agency. Another yet-to-be-awarded contract, for capital construction, is worth $600 million, USAID spokeswoman Ellen Yount said.

USAID won't officially release the total value of its Iraq plans until winners have been determined for all eight, a task that should be finished by the end of March, Yount said. But last week someone in the U.S. government leaked documents to The Wall Street Journal, which reported that the $900 million "mother contract" for Iraqi reconstruction has five bidders, all U.S. firms and among the largest engineering companies in the world: Fluor; Halliburton's Kellogg Brown & Root subsidiary; Bechtel; Louis Berger Group; and Parsons.

Fluor and Halliburton are the only publicly-traded companies in that quintet. Along with Bechtel, they're widely viewed as the strongest candidates for overseeing work in Iraq after the war.

"This is a large potential positive for Fluor," Salomon Smith Barney analyst Leone T. Young wrote in a research note last week. "The timing, funding and final outcome of the contract remain unknown at this point in time. ... Nevertheless, we think this underscores Fluor's likely characterization as a 'rebuild Iraq' play, and the stock may well trade up with any positive indications of a swift, successful Iraqi confrontation."

Whether the stock should trade up is a separate question.

Fluor reported $10 billion in annual revenue and $9.7 billion in backlog for 2002. That kind of financial base wouldn't get much of a boost from a $900 million deal over two years, and there's a strong possibility that any single contractor will end up with less, since the U.S. government often divides these projects between multiple vendors.

Bear Stearns analyst Michael Dudas guesses that a $500 million contract eventually might add 5 cents to Fluor's earnings per share. It's not much for a company that earned $2.13 per share last year.

Fluor typifies its peer group of multinational engineering firms, all of whom routinely deal with billion-dollar contracts. Any company that qualifies for a major reconstruction project in Iraq is large enough that it doesn't need the deal in order to thrive as a business. "There are reasons that you’d want to own Fluor or buy Fluor as an investment that have nothing to do with Iraq," Dudas says. "But I would not suggest somebody say 'I want to buy Fluor stock because they’re going to rebuild Iraq.' I don’t think that’d be the right advice."

USAID's contracts cover humanitarian work such as paving roads and building schools, but Iraq's other potentially large source of business might be petroleum-related structures. Some stock traders are already speculating on it, judging by the steep climb in the stock price of Boots & Coots International Well Control, whch handled oil fires during the Persian Gulf War in 1991. Not that it took much to drive Boots & Coots higher -- as recently as last week, it was a penny stock and understandbly so, since the company is teetering on the edge of bankruptcy.

Halliburton is often mentioned as a beneficiary of Iraq rebuilding, because it can take part both in humanitarian construction (through Kellogg Brown & Root) and oil activity, through an oil services arm that is the world's second-largest, behind only Schlumberger. But Halliburton shares have been almost paralyzed for the past several months because of the firm's asbestos liability suits; the company last week said it reached an agreement with 75 percent of plaintiffs, but shares have only risen slightly since that announcement. Meanwhile, Schlumberger has been weighed down by debt the last couple of years, largely tied to a $5.1 billion acquisition of a software firm in 2001.

Oil services companies' overall health notwithstanding, it could be too early (and in the case of Boots & Coots, probably too dangerous) for individual investors to make Iraq-related bets on the oil business, because no one knows what will be required. Will Saddam set his oil fields on fire? How much collateral damage will be suffered in the fighting? And how much did Iraq's oil structure suffer -- if it did at all -- from the country's isolation of the past 12 years? Until those questions are answered, any estimates for oil-related work are only guesswork.

Ultimately, Halliburton and Schlumberger present the same problem for investors as Fluor and its ilk: they're already huge. For all their problems, Halliburton and Schlumberger each pulled in more than $13 billion in revenue last year. And even if one of those Iraq-oil-rebuilding guesstimates -- including $1.5 billion (Deutsche Bank), $3 billion (Cambridge Energy Research Associates) and $5 billion (Council on Foreign on Relations) -- are correct, the money probably will be divided between several companies, some of which don't trade on American markets, such as Russian and French oil firms that already have Iraqi contracts worth billions of dollars. (You didn't really think France and Russia are opposed to Iraqi war only for humanitarian reasons, did you?)

Speaking of foreign companies, don't be surprised if they get a significant chunk of rebuilding work. Although Bush administration officials are promoting a U.S.-led reconstruction effort on grounds of speed and efficiency, members of Iraqi opposition to Saddam Hussein recently told Dow Jones Newswires that U.S. companies will not be guaranteed any oil-industry business. And British firms are already clamoring for large subcontractor roles in postwar Iraq, especially given their country's diplomatic and military support of the United States.

Analysts point out that in engineering and construction firms saw their share prices rise before the 1991 Gulf War, largely because of predictions that Kuwait would need billions of dollars in construction work. Most of that business never materialized.

"There are a lot more questions then answers in the near term," Dudas says of the prospects for Iraqi business. "It could take many years, if not maybe even a decade, to fully benefit from that. ... I’d be a bit more cautious rather than aggressive looking at the rebuilding opportunities in Iraq."

-- Sergio G. Non is the online editor of Wall $treet Week with FORTUNE.