Marjorie Cates had not planned on starting over as a temporary receptionist at age 58.

But when she was laid off by Northrop Corp. from her job as a graphics coordinator, the ebullient, white-haired woman quickly discovered that Kelly Services, the temporary placement firm, was one of the few ready sources of employment for an older person with a narrow range of skills."I'm alone in the world and I need to earn my living," said Cates, pausing amid a busy morning of answering phones and paging co-workers at the Los Angeles County March of Dimes office. "At this point I take what I can get and make the best of it."

For Kelly Services, it's a perfect match. Desperate - as are other temporary placement companies - to satisfy employers' mounting demands for temporary workers, Kelly is reaching out to older people for help filling the job orders.

"The working world needs these people," said Charlotte Schwartz, a Kelly district manager in Portland, Ore., who describes herself as "65 and over" as she tours the country urging older workers to sign up with the firm, which is based in Troy, Mich.

Demographic trends have forced temporary placement companies to heap new attention on senior citizens. Young people are a shrinking portion of the labor pool, while the elderly are the fastest-growing portion of the population.

"The so-called `baby bust' is upon us," explained Thomas Anton, executive vice president of Kelly.

The result: To attract older workers, temporary agencies such as Kelly are sending recruiters to speak at meetings of retirees, working with the American Association of Retired Persons and other senior citizen organizations and holding special events aimed at the senior population.

To the older worker, temporary agencies may offer training on new office equipment - word processors and personal computers, for instance - that wasn't around during the senior's earlier working life. To the employer, they emphasize that an older worker may bring the kind of dependability, experience and resourcefulness that might be lacking in a younger temporary.

"One thing I'll never understand is why companies ask people to retire at 55," Schwartz said. "To me, they are letting go invaluable experience. The reason for it is they can get younger people at a lesser price. But how can you equate that? How long does it take to get a younger person up to that level of experience?"

In fact, many employers actively seek out older workers. About 40 percent of the companies that contacted Careers for Older Americans during a recent period said either that they preferred to hire older workers or sought employees possessing the reliability and knowledge associated with older people.

March of Dimes director Anthony F. Giacalone said his experience with older workers such as Cates was consistently positive.

"They're hard to ruffle and add a real sense of stability," he explained.