A smorgasbord of benefits offered by only a few firms

In the pension business, some have hailed them as the greatest thing since sliced bread. But so far, the loaves have been slow to move off the shelves. They are flexible benefit plans, sometimes called ''cafeteria plans.''

They give employees a choice in picking their own benefits, letting them select from a range of retirement and compensation options. A worker can take less of one benefit, like vacation time or dental coverage, in return for more of another, like money in their pension fund.

Most of the plans include programs for retirement savings; but a few do not.

''We don't have any retirement program in our plan,'' said Michael Corrigan, director of compensation and benefits at Morgan Stanley, the investment banking firm. ''It's too cumbersome and costly to do all the actuarial work and computer programming.''

Whether they plan to include retirement saving programs or not, these complications have been enough to make a lot of companies take one look at flexible benefits, and drop the idea.

With almost every employee having their own ''tailor-made'' program, the bookkeeping chores for the company are akin to a big-city department store making a different suit for each customer.

''I've seen a big surge in companies that say they are interested in setting up flexible plans,'' said John Dirlam, a principal with Towers, Perrin, Forster & Crosby, pension consultants. ''But when they explored it in depth, they've backed off.''

''I can't think of more than 10 companies that have fully implemented flexible plans,'' he added.

''Philosophically, I favor the idea,'' said Carson E. Beadle, director, New York region, William M. Mercer Inc., pension consultants. ''But I've seen enough problems to be cautious.''

These problems, he says, include the high costs of administration and communication, providing employees with easy-to-understand information on the complexities of benefits planning, and the administrative burdens of adding variations to the plans as employees seek greater flexibility.

This last problem has caused a number of flexible programs to collapse, Mr. Beadle says, because of the wide variety of choices, frequent changes in benefits, and the troubles involved in validating insurance claims against the coverage in force at the time. A worker may have been moving in and out of full dental coverage, for instance, and not be covered at the time major dental work was done.

With all the drawbacks, employers that have installed cafeteria plans have found there are advantages. For one thing, they get a better return on the money they spend on compensation, because they are able to target benefits. In doing so, they don't have to spend money on full benefits for everyone; just those who want them.

For employees, flexible benefits help fit into a variety of personal situations: two-earner families, divorced or widowed workers, women reentering the work force, different attitudes toward early or deferred retirement, and changing ideas about saving and security.

Besides Morgan Stanley, companies that have implemented flexible benefit programs include Educational Testing Service, American Can, TRW, Girard Bank in Philadelphia, Northern States Power Company of Minnesota, and the State of Alaska. In addition, LTV Corporation, Loew's Corporation, Arcata Corporation, and Johnson Controls are either committed to adding flexible programs in the near future or are reported to be planning to add them.

A recent survey of more than 500 corporate chief executive officers by William M. Mercer found that 36 percent had examined flexible benefit programs, while 40 percent had not. Only 32 percent said they considered these programs an important consideration in benefit planning. Sixty-four percent either did not consider it important or had no opinion. The other 4 percent did not answer the question.

One reason for the slow growth, Mr. Dirlam and others say, is that cafeteria benefit programs are complicated to start and maintain.

For instance, ''there is no (computer) software program for it,'' says Mary Jane Klansly, director of employee benefits at Educational Testing Service in Princeton, N.J. In 1974, ETS became one of the first US companies to put in a flexible plan, Ms. Klansly said.