You've just been offered a challenging new job and must sign and return an offer letter within a week. The letter states that you'll be an employee at will, subject to termination on two weeks' notice. It doesn't specify severance but bars you from competing with your employer for two years after you leave. Can you change the terms of your employment?

"The ball has traditionally been in the employer's court," says Loren Allison, a partner in Rothberg & Logan, a Fort Wayne, Ind., law firm. "However, potential employees with marketable skills now have much more leverage."

Executives and professionals who were laid off or are voluntarily leaving secure positions for unknown territory hope to swing the balance of power in their favor. While golden parachutes that guarantee departing executives several years' pay are generally reserved for CEOs and athletic coaches, there's room to maneuver at lower levels as well.

"A candidate can ask for anything and everything," Mr. Allison says, "but you have to decide how you can do it softly and tactfully."

Written employment agreements may be multi-page contracts or simple letters. If you're wondering what to ask for, consider these options and negotiable provisions:

Formal contracts are typically used only at the highest levels, according to a 1992 survey by Hewitt Associates, a Lincolnshire, Ill., consulting firm. While 82% of surveyed companies offered contracts to their CEOs, only 35% covered more than ten executives.

Although the survey is outdated, Hewitt consultant and attorney David Kompare says the results are still valid, with one difference. "Employees may have more leverage today than in the recent past," he says.

Gaining a contract from a company that doesn't typically use them is difficult. And if you agree to work for an employer that provides generic agreements for all executives, you may have to accept terms you dislike, such as a noncompete provision, says Mr. Kompare. Nearly three-quarters of survey respondents include noncompete provisions in their contracts, because, while they're difficult to enforce--"Courts hate to restrict the exercise of capitalism," Mr. Allison says--companies view them as insurance against defections.

Before asking for an agreement, consider the pros and cons, says Stacey Cushner, an employment lawyer with Bernstein, Cushner & Kimmell in Boston. On the plus side, having an agreement protects you from being terminated arbitrarily. On the negative side, you'll have a hard time leaving a job you dislike.

"People who think it's great to have a secure employment agreement don't think about that," she says.

Priscilla Claman, president of Boston-based Career Strategies Inc., an employment consulting firm, recommends viewing an employment agreement as career risk management. For instance, an executive who leaves a job at a successful biotechnology firm on the West Coast for a start-up organization in the East risks the loss of his reputation and network of contacts. In this case, the executive should determine how long it would take to become re-established if the new position doesn't work out and ask for an agreement specifying severance for that period, she suggests.

CEOs hired to complete turnarounds usually want and receive golden parachutes because their jobs are so risky, Ms. Claman says. "You're subject to the vagaries of the board, and hardly anybody can turn a company around in one or two years," she says. "If you fail, it's a huge risk to your reputation."

Less-senior executives who are asked to tackle risky assignments also are more likely to receive contracts, Ms. Claman says. A human-resources director received a contract because his new company was a takeover target, she says.

"When there's an obvious risk to your position continuing to exist, that's a reason for having a contract," she says. "Even a senior engineer joining a company about to be acquired can point to such a risk."

A star programmer who joins a small software company also is likely to gain a contract because his work is critical to the company's success, says Mr. Kompare. "You have more leverage because you're a bigger piece of the pie," he says.

Large stable organizations prefer to limit contracts to the senior team and give other candidates offer letters that reflect the terms they negotiated, says Mr. Allison. These documents can serve the same purpose as a contract since they're legally binding, he says.

"Sometimes it's better to stay low key," he says. "After you've negotiated, you can write a simple acceptance letter which reflects your understanding that you're willing to come to work based on A, B, C and D."

If you receive a standard offer which doesn't specify particular items you discussed with a prospective boss, call to ask for a letter confirming those terms, says Barbara Collins, account manager in Berwyn, Pa., for Drake Beam Morin Inc., a national outplacement firm. Few employers object to such a request, she says.

"After you've talked and nailed down what you're going to get, I'd say, 'I appreciate your sending the original offer in writing. I'd also appreciate your sending me a letter confirming what we just talked about,' " Ms. Collins says.

Many executives don't think to ask for an agreement after a promotion, but having one at this point can protect you and your employer, says Mr. Allison. Consider that when you first joined the company, you may have only agreed to abide by the handbook. "Now that you're a vice president and questions arise about trade secrets, your attorney can say you're not bound by anything," he says.

If your employer won't give you a letter, prepare a memo outlining your short-term job responsibilities and have it signed on your first day of work, says Ms. Claman. Include the responsibilities and objectives you discussed before you were hired. This way, if the person who recruited you leaves, you can point to what you were supposed to accomplish in your first three months in case "something horrendous occurs," she says.

One executive used this approach after being hired by a mercurial boss to manage several departments. "She found after a few months that she couldn't work there," says Ms. Claman. "She brought her memo to human resources, pointed out that her boss hadn't abided by its terms and was awarded severance pay."

For executives in high demand, anything is negotiable, says Ms. Cushner. Detemine what you'd be happy with and what you're willing to accept in a new job. This is your bottom line, she says.

Many executives focus on termination provisions. For instance, a chief information officer with Internet expertise who was offered two positions at good firms based his decision on the severance he negotiated, says Tod Gregory, a partner in San Francisco with Korn/Ferry International, a New York-based search firm. When one company offered three years' pay if the job didn't work out, he accepted.

At his level, "that was unusual," since most executives only receive a year's severance, says Mr. Gregory.

Agreements often focus more on termination issues than on employment. "Five to eight pages of a typical ten-page contract deal with termination provisions," says Mr. Kompare. "They spend little time talking about ongoing employment."

If a company has a formal severance policy -- and most large firms do -- a separate severance agreement may not be necessary. You also may not be able to exceed the plan's provisions, says Mr. Kompare. "I'm not going to be able to insist on something different unless I'm very senior or have unique talents," he says.

Termination provisions also might include outplacement assistance, career counseling and supplemental benefits. For instance, you could ask the company to continue your insurance benefits after you're terminated or provide you with additional compensation to cover it. Also ask if you can keep investing in the 401(k) plan and other deferred compensation plans, says Mr. Allison.

To ensure continued income and circumvent a noncompete provision, request a consulting contract if you're downsized, he suggests.

"Noncompetes are hard to enforce, and your employer may be concerned that you'll go to a competitor and kill them," he says. "If they give you a consulting contract for two years, everybody wins."

Agreements may deal with specific risk factors. For instance, an employee who's moving to another coast might ask to be compensated for moving back if he or she is separated for any reason, says Ms. Cushner. Such a payment would be in addition to regular severance.

Consider the specific terms you need to be successful in a new position. Compensation falls under this category and is relatively easy to negotiate, says Ms. Collins. Before stating an amount, know your needs and what's competitive for someone in your position and company type.

Knowing your market value is key to negotiating from strength, says Mr. Gregory. Indicators include the way your current company treats you and if you're being offered expanded opportunities, whether you're in a hot area and doing an outstanding job and whether you've taken on added responsibility.

If the company can't budge on pay levels, ask for more vacation or a sign-on bonus. "If you can only move the salary so much, ask about a bonus to close the gap," says Ms. Collins.

Extra benefits are difficult to secure since most benefit plans are regulated, she notes. However, you can ask to have the waiting period for enrolling in a 401(k) plan reduced, or to be provided with memberships, computer equipment, a company car or a car allowance, depending on the relevance of these perks to your job.

If you're relocating, know the typical perks provided to executives in your new area. Visit the company's web site and review annual reports, proxy statements and other documents. "We have a particular challenge in the Bay Area because of the cost of living, and a candidate who is sharp enough can be taken care of when moving in," says Mr. Gregory.

Before finalizing your letter or document, ask an attorney who specializes in employment law to review it. Find out what each provision means and what else you should negotiate before signing. However, don't flaunt your attorney to your new employer or "they'll respond to your lack of trust," says Ms. Claman.

In lieu of an attorney, discuss the agreement with an executive recruiter. These professionals know what's reasonable to request and what can break a deal.

The best time to negotiate is after you receive an offer. "It's not only acceptable but prudent to ask for time to review it," says Ms. Collins. Be sensitive to the company's hiring pressures and don't delay excessively. "When you ask for time, always preface it with 'I'm delighted to receive this offer,' " she says.

Be prepared before returning to the table. Know what you want and ask for it in one session, so you don't return for more.

"Do it all at once" or the offer may be withdrawn, says Ms. Collins. "If you keep saying, 'I forgot this' or 'I forgot that,' you'll appear disorganized and it speaks volumes about how you'll be as an employee."

When making requests, be tactful and courteous. Say, "How would the company feel about this?" rather than "What can you do for me?" Make your requests in order of preference and present them as business propositions.

"You stand a better chance of getting what you're asking for if you demonstrate a business need for it," she says. "Saying 'It'll make me feel better' doesn't work. Preface your requests by reviewing the nature of the job, reminding the employer how fabulous you are and how smart they are to have made the offer."

Be especially positive when discussing termination provisions. One approach might be to say, "I'll stay with you and do the best job I can for you, but I need to make certain that if I'm terminated it's for a good reason and I'm protected," she says.

The negotiation process can set the stage for a good working relationship, so try to keep discussions friendly. "You want to make sure that the first day of work is an absolute high," says Ms. Collins.

--Ms. Mende is a freelance writer in Waltham, Mass., who specializes in career issues.