Welcome to the "Twilight Zone," the time between when a career ends and real retirement begins.

Increasingly, American workers are finding that early retirement offers start rolling in by the time they turn fiftysomething -- long before they had considered making golf a full-time pursuit.

So, it's never too early to worry about what you will do next in your career since by age 40 you technically are considered an "older" worker and by 50 you might be history at many big companies.

In fact, the Commonwealth Fund, a philanthropic organization in New York that has been studying older Americans at work, reports that a third of career jobs now end at age 55 and almost half are over by the age of 60. Moreover, the fund says, "few older workers are aware of this prospect; even fewer are prepared to deal with it."

When the ax does fall, many early retirees never return to the labor force. But there are nearly 2 million workers aged 50 to 64 who are ready and able to go back to work, according to a national survey recently conducted by the fund.

Those who do want to work, the survey showed, are an employer's dream: They say they don't mind seasonal work. They don't mind being on their feet. They will commute more than 30 minutes. Working alone is all right with them, and about half said working evenings and weekends is not a problem.

One of those workers to waste no time in returning to the work force was Edward J. Kane. At age 55, Kane left his desk at International Business Machines Corp. in New York at 7 p.m. on a Tuesday night and the next morning was in Atlanta for his new job as a vice president for Dun & Bradstreet Software Services Inc., a computer applications software company.

"It really hit me between the eyes," said Kane, who was corporate director of quality for IBM. "I was at IBM for 30 years and I was very happy."

Kane's situation is typical of what happens to older workers when they are reemployed: Many go to smaller, more entrepreneurial companies that are hungry for their experience. But Kane's case is atypical in that he never had to forsake his professional ambitions and never went without a job.

Many other fiftysomethings find it more difficult to get back into the work world for a number of reasons.

"They have a tough time coming down in responsibility and income," said Joyce Schuman, manager of the Virginia Employment Commission's Job Service. "Then couple that with age discrimination."

Schuman said her agency loses track of many early retirees because "we don't have the kinds of positions they are looking for."

Another big barrier to reemployment is that some older workers insist on finding "clones of their old jobs," said Helen Axel, senior research fellow with the Conference Board in New York.

What those who have taken early retirement need to come to terms with quickly, Axel said, is that life as they knew it is over. If the company they had been working for is willing to offer them some kind of a job once they retire, it most likely will be temporary or involve contract work that the company can control.

"Their {the companies'} interest is in severing the career employment relationship with an older person and then reconsidering it on a different basis," Axel said. "A lot of these people get back to work in one way or another though they construct a very different work life."

But things may be looking up for the older worker, said James E. Challenger, president of Challenger, Gray & Christmas Inc., an outplacement firm in Chicago. "These people are getting jobs as quick, or quicker, than we have ever seen them do it," he said.

The median time it takes for a job seeker of any age to land a position is three months. Workers age 50 and over are now doing it in 3.3 months, said Challenger. It used to take them at least four months with the help of outplacement specialists.

But it takes some attitude adjustment, like willingness to go to a smaller company, as Kane did.

Challenger said many small- and medium-size companies want people who can produce immediately and -- surprise -- they welcome people who will stay for the long haul.

It may sound like something out of the "Twilight Zone" to older workers out of a job, but Challenger said it does happen.