(FORTUNE Small Business) – Harold Nelson, an Army reservist, knows all too well the cost of patriotism. In 1991 this optometrist from Louisville was just opening his private practice when the Army tapped him to help with Operation Desert Shield against Iraq. What's more, the military offered no financial support to protect his business. Stationed at nearby Fort Knox, he applied to "moonlight" at his own practice ten hours a week but netted less than 25% of his previous revenue. Owing for rent, equipment, and malpractice insurance, he couldn't make enough to avoid bankruptcy. Nine years later Nelson is still paying off his debts.

At press time U.S. reservists faced a possible return to Iraq. As of early February, 112,000 National Guard and Reserve troops have been called to active duty. But whether or not they are activated this year, one issue has become very clear for entrepreneurs who serve. In addition to the usual concerns about personal safety and the security of their family, they face the question of whether their business can survive without their most valuable and irreplaceable asset: themselves.

To Jeff Forrestall, the risk of heading to war seemed remote when he enlisted in the Army Reserves in 1994. For seven years Forrestall happily gave his "one weekend a month and two weeks a year" in exchange for a little pay and camaraderie. But that rosy worldview changed on Sept. 11, 2001, and one month later Forrestall, managing partner of a 16-employee accounting firm founded by his father, was sent to Kuwait. Making matters worse, the call-up came just three months after Forrestall and his wife spent $3 million to open a 30-employee franchised day-care center. During his seven months in Kuwait, Forrestall forwent $150,000 in salary and took out a $120,000 loan to keep his businesses afloat, and he's worried about the hit they'll take if he's called up again.

Early this year reservists were scrambling to plan for a feared call-up. But preparation can accomplish only so much. Naval reservist Steve Kaufman of Jacksonville left town for four days to see whether his four-employee public relations firm could maintain the client base. He didn't like the results and hopes some adjustments will do the trick. Mark Herndon, president of Talicor Inc., a Hayesville, N.C., board game and puzzle maker, has devised two parallel business plans--one if he stays, one if he is called up (less manufacturing, more purchasing). As one of the top ten employers in his rural county, the government will give Herndon an extra two weeks to prepare should he be tapped to serve, but that doesn't do very much to allay his concerns. "Every time the phone rings," he says, "I'm a little jumpy."

Of course, these men are volunteers, and uncertainty is part of the job description. But most other reservists are afforded some security. The Uniformed Services Employment and Reemployment Rights Act requires an employer to hold reservists' positions and, upon their return, restore their jobs without penalty. That doesn't do very much for the people who run small businesses; when entrepreneurs are called, the question is not whether their job will be there in a year but whether the business they built will still be viable.

This year the government finally appears to be paying serious attention. Albert Zapanta, chairman of the Reserve Forces Policy Board at the Department of Defense, admits that so far the problem has fallen through the cracks, but says that discussions of a possible remedy are gaining momentum. "You'll see more and more focus on small business as we start to get feedback, unfortunately, for what we didn't do." The Small Business Administration, too, is scrambling to study the problem and prepare its staff to offer advice and solutions. "We know this wave is coming, and we're taking this seriously," says William Elmore, head of the SBA's Office of Veterans Business Development. "The highest levels of the agency are involved in making sure we do this right and well and as quickly as possible."

Still, workable solutions won't be easy to find. In 2001 the SBA announced that low-interest disaster loans of up to $1.5 million would be available to cover small business losses due to call-ups. But the response to the program has been underwhelming at best; to date only 32 loans have been granted, perhaps because small business owners are reluctant to saddle themselves with debt, particularly when they have no way of knowing when they'll be able to return to work.

And loans may help, but they won't solve entrepreneurs' greatest fear: that when they leave, their businesses will suffer from the brain drain. "Being a CPA, I'm not selling product, I'm selling me. And I can't replace me," says Forrestall, whose business stalled when he served in Kuwait. The prospect of fleeing clients is troubling to Steve Kaufman. "I won't do too much growing while I'm gone, but hopefully I won't lose accounts," he says. "My staff needs to keep the current clients happy and keep the business going. It's all I have."

One possible solution was presented in a 1993 report from the Department of Defense, although it was largely ignored after its publication: mobilization insurance. The report found that over a third of enlisted members and over half of officers indicated that they would buy mobilization insurance if monthly costs were kept low enough. But here, too, problems arise, since the military can't tell private insurance companies how many reservists would be affected or forecast the likelihood of mobilization. The task of underwriting the risk may well fall to the government.

But if the government can't figure out a way to safeguard his business, Jeff Forrestall expects that he'll need to resign from the Reserves (once he's able--in this uncertain climate, he's been told, he cannot leave). "I enjoy being in the Reserves, and I want to serve my country," he says. "At the same time, when the costs get up there, it starts making things a lot more difficult. It gets to be a lot to sacrifice in the end."