In theory, the widespread availability of temporary professional workers is a small-business owner's dream come true. You can hire everyone from cost accountants to road-and-tunnel engineers for as long as you need them. When your special project is finished, those temps conveniently disappear. And with professional temps, "there's enough do-it-on-their-own attitude that I can assign a task and not worry about it being done," says Peggy Brown, accounting manager of software publisher Aldus Corp., in Seattle.

Consider two main areas in selecting a temp-help company: its basic characteristics and the way it screens its temporaries. Is it really a temporary-help company, or is it an executive-search operation? If it's the latter, your "temporary" worker may not qualify as an independent contractor under Internal Revenue Service rules. A temporary-help company can usually fill a position much more quickly -- within hours -- than an executive-search company can.

Make sure the company has been in business for a while. A seasoned firm should be able to guarantee an immediate replacement if you're not happy with the professional it sends over. If a temp will be working with proprietary information, will he or she sign a confidentiality agreement? Look also for a firm that specializes in the discipline you're seeking. Its placement counselors should themselves have experience in that particular field in order to accurately gauge your needs.

Next, turn your attention to the quality of the firm's temporaries. The higher the company's selection standards, the better. The fact that a worker has been tested, for example, shouldn't necessarily reassure you. Job experience is more important. The firm should have checked previous jobs, references, and other credentials.

When it comes time to use a temporary, beware of the pitfalls. Aldus's Brown says she felt that temps placed an extra burden on her. "In a fairly long-term assignment you usually don't find out what a temporary can really do until a significant amount of time has elapsed," she says. "As a manager I'm taking more time to do stuff that I would delegate if I had a permanent worker."

And though temporaries are generally cheaper than regular employees, there can be hidden costs. Brown says overtime costs, which she wouldn't incur with a permanent employee, can add substantially to the bill. In a tight market, it's worth trying to negotiate a cheaper rate.

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Temp Rates Average hourly earnings for professional temporary workers vary from region to region. According to the Bureau of Labor Statistics, a seasoned accountant or auditor can expect $12.78 an hour in Boston but only $8.99 in San Diego. Engineers average $26.10 in Indianapolis, but expect $29.11 in Seattle. Computer programmers pull in $18.04 an hour in Houston, but in San Jose, Calif., it's $22.33.

-- Ellyn E. Spragins

To find out which temp-help companies serve your area or to request a free directory, contact the National Association of Temporary Services, in Alexandria, Va., at (703) 549-6287.