NEW YORK (AP) - When Enron Corp. and WorldCom Inc. collapsed into bankruptcy several years ago, their employees lost billions as the company stock in their retirement accounts became all but worthless. Now, employees of Bear Stearns Cos., the troubled New York investment bank, face a similar fate because their compensation included heavy doses of company stock.

It is yet another reminder that workers should be very cautious about their company stock holdings.

Mike Scarborough, president and chief executive of The Scarborough Group, a firm in Annapolis, Maryland, that manages retirement account monies for workers, recommends that workers who get company stock should trade it or sell it at their earliest opportunity.

"I've come to believe that people should never hold stock in the company they work for," Mr. Scarborough said. "It creates too much risk because they already have their paychecks coming from the company, their benefits, and they may have a pension coming from the company.

"That means holding (the company's) stock, especially in their 401(k) plan, is just foolish."

Workers come to own company stock in a variety of ways. In many cases, big corporations match employee contributions to company-backed 401(k) retirement plans with corporate shares. In other cases, such as at Bear Stearns, shares are given as bonuses or as part of compensation packages.

When accounting frauds brought down the energy trader Enron in 2001 and telecom company WorldCom the following year, workers' retirement holdings lost almost all their value.

At Bear Stearns, employees own about a third of the bank's outstanding stock.

The share price has fallen from a peak of $172.61 in January 2007 to about $5 this week. JPMorgan Chase & Co. has bid just $2 a share to take over the company. Bear Stearns' press officer did not return calls seeking comment.

Such heavily publicised cases have prompted many savers to rethink their corporate stock holdings.

The nonprofit Employee Benefit Research Institute (EBRI) in Washington DC, said its most recent survey of assets in 401(k) plans found that the portion in company stock dropped to 11 percent in 2006 from 13 percent in 2005. Company stock holdings stood at 19 percent as recently as 1999, EBRI said.

On the other hand, in the plans that have company stock as an option, some 7.3 percent of workers have 90 percent or more of their 401(k) assets in company stock.

Why?

"People think that what happened to Bear Stearns and other companies that go belly up only happens to someone else's company, not their own company," Mr. Scarborough said. "That is, until it happens to their own company."

Pamela Hess, director of retirement research at Hewitt Associates, a global outsourcing and consulting firm based in Lincolnshire, Ill., said about half of mid-size and large companies offer company stock for workers' retirement plans, but that employee holdings of company stock have been dropping in recent years.

Some of the decline is because fewer of the companies with an employer stock investment option match exclusively with company stock - 23 percent in 2007, down from 45 percent in 2001, Hewitt surveys have found.

In addition, Hewitt says companies have sped up the timetable for the unconditional transfer, or vesting, of company shares, so workers can sell them or trade them sooner than in the past.

The problem, Ms Hess said, is that many workers don't make any changes at all in their 401(k) holdings, which means they hold any company stock they get.

"They're often not very sophisticated about investing and they don't understand the risk of holding a huge block of a single stock," Ms Hess said.

If a worker has a diversified portfolio and one component falls, it will not be too painful, she said. But if the holdings are concentrated in a single stock that falls, it will be felt substantially, she added.

Ms Hess said most experts advise "that you shouldn't have more than 10 percent of your portfolio in a single stock" and believes that should be the maximum for company stock holdings.