If you're counting on an inheritance from your parents to rescue your underfunded retirement plan, you could be playing a dangerous game.

Despite predictions of a massive transfer of wealth between generations, many baby boomers can expect to get little or nothing from their parents.

Economists and financial experts can't agree on how much money baby boomers and their offspring are likely to inherit. In fact, their predictions of the total sum involved vary widely. But many agree that a small number of wealthy families are likely to receive the bulk of the windfall, and that many other would-be heirs will end up disappointed.

About 64 percent of those who receive bequests of $100,000 or more are already well off, ranking in the top quintile of net worth, according to an AARP study analyzing the Federal Reserve Board's 2001 Survey of Consumer Finances, the most recent figures available. The median inheritance baby boomers received was about $48,000, but 83 percent of them said they'd received no inheritance to date.

"It's fair to say that expectation is greater than reality," says Paul G. Schervish, director of Boston College's Center on Wealth and Philanthropy. The Center estimates that at least $45 trillion will be disbursed by estates over the next five decades, though others argue that projection is too high.

For those who do inherit something, it's often not as bountiful as they had hoped. A big portion of large estates goes to pay taxes and is bequeathed to charities, according to Mr. Schervish. And there are some hints that the inheritance pie may get sliced even thinner.

Living longer. Increasing longevity is a primary reason for many of today's inheritance letdowns. A 65-year-old man today is expected to live to age 81, while a 65-year-old woman should live until 84 -- nearly two decades beyond typical retirement age. Most wealth goes to a surviving spouse before it reaches children or grandchildren, so some heirs are well into retirement themselves by the time an inheritance arrives.

It's not unusual for a once-$1 million nest egg to be whittled down to almost nothing. Health-care costs are soaring, and nursing home bills run over $100,000 annually in some parts of the country. About 40 percent of those 65 and older will spend at least a short time in a nursing home, according to AARP. Many more will spend their final years in assisted-living centers, which at the highest levels of care can rival nursing home costs, AARP says.

Dan Littell, 63, of Plainfield, Ind., saw it happen. His mother entered a nursing home six years ago with more than $400,000 left from his father's estate. She spent $6,000 a month in nursing home bills and prescription drugs in her last few years, and left around $200,000 to her son when she died at age 94 last year. Losing the inheritance money wasn't a big deal, he says, but it persuaded him and his wife to buy long-term care insurance "so our children won't have to experience the same thing we've gone through."

Making it last. Another culprit: the annuitization of a greater share of retirees' financial resources, which is eating into wealth they might otherwise bequeath, according to a 2000 report by the Federal Reserve Bank of Cleveland.

When considering traditional pension income, Social Security, Medicare and other government benefits, about 50 percent of all financial resources of those 65 and older was annuitized in the 1990s, versus 20 percent in the 1960s. While a large portion of that was not by choice and paid through income taxes, a growing share today is voluntary: Many retirees are now using their savings to buy insurance products, such as fixed annuities, that guarantee fixed monthly payments for life in exchange for handing over a lump sum. Others are taking out reverse mortgages, which allow them to borrow against their home's value without making any repayments during your lifetime.

Giving it away. Even aging parents with ample wealth to pass along aren't necessarily leaving it to their kids. Surveys suggest that boomers and their parents are often opting instead to give more to charity or spend it all themselves. Others are passing along their wealth to their family before they die, often as an estate-planning technique.

For would-be heirs, the lesson is clear: You can never be sure of any inheritance.

Jarah Tuttle, 35, a real-estate agent in Greenwich, Conn., and her family expected to receive a seven-figure inheritance from her uncles, who owned a successful insurance business. The last surviving uncle, however, left the money in a trust for a girlfriend in Florida, naming the family as the ultimate beneficiary. The girlfriend lived for over a decade off income from the trust and the remaining $420,000 or so was divided between eight family members. "I guess it was his money," Ms. Tuttle says. "Though we didn't know it was going to work out that way."

Getting real. To thwart such inheritance surprises, older generations should discuss inheritance expectations with their heirs, says Timothy Wyman, a tax attorney and certified financial planner in Southfield, Mich. But parents don't always feel like their children should have such foreknowledge -- making it difficult to really prepare. And parents themselves don't know what the future holds.

Mr. Wyman says when clients anticipate an inheritance and want it factored into their retirement forecasts, he'll do it, but "I usually discount it." he says. "If a client says Mom and Dad have a net worth of $2 million, for planning purposes, I'll just assume you receive 50 percent of that amount."