Bank stocks have been bludgeoned this year, federal regulators are worried about a nationwide deposit insurance problem, and some of the biggest banking companies are feeling financial pain.

Yet the canny Tisch brothers -- Laurence, the CBS Inc. chief, and Preston, the Loews Corp. executive -- have been buying up the stock of banks lately as if they knew something the rest of the investment world doesn't.

Last Monday, the Tisches disclosed they had raised their stake in Bank of Boston Corp., the third boost of their holdings in that troubled New England bank since December 1989.

And last month the Tisch brothers and other family members disclosed they had acquired sizable stakes in three other bank holding companies: Boston's Baybanks; Pittsburgh's Equimark Corp.; and Chicago's Continental Bank Corp.

"Banks are being hammered right now. Bank stocks are declining very rapidly. Our index of bank stocks has gone down 30 percent just since June," said James Marks, a partner in SNL Securities, a bank and thrift research company based in Charlottesville, Va.

On Thursday, the SNL Bank Index, which measures the securities of 380 publicly traded banks, closed at 66.1. On June 7, it stood at 92.

"What the Tisches are doing is high-risk investing," said Marks, noting that they have taken chances and done well before. "Which is exactly why people like myself are hesitant to criticize them."

Marks said he thinks the revelation earlier this month that the Federal Deposit Insurance Corp. is in trouble may be only the beginning of the bad news.

A congressional watchdog report said the FDIC, which guarantees commercial bank deposits up to $100,000, is underfunded and could require a savings and loan-like cleanup if Congress doesn't do something to prepare for a rash of bank failures.

"I think bank stocks are going to continue to have a hard time for the foreseeable future," Marks said.

In another sign of trouble in the banking world, giant Chase Manhattan Corp. on Friday revealed plans to bolster its cushion against bad loans, halve its dividend and slash its work force by 5,000 jobs, which will result in a large loss for the third quarter.

While most investors are shying away from bank stocks, the brothers Tisch are buying, and analysts say the wealthy siblings -- Forbes magazine has estimated their family's fortune at more than $1.7 billion -- have the time and money to buy low now and wait for banks to be a good investment again.

"The general feeling is that the Tisches have a well-deserved reputation for investing and making money, particularly that they are very successful at bottom-fishing," said James J. McDermott Jr., a banking analyst with Keefe Bruyette & Woods in New York.

"The general feeling about the banking industry remains that it is an industry under siege because of asset quality problems," the ratio of a bank's total assets to its high risk loans in real estate and construction, McDermott said, adding: "But the patient money is likely to be rewarded in the long term."

"That's how you make money," banking analyst Bucky Rulon-Miller said. "Throughout history, successful investors have been people who buy their straw hats in January," said Rulon-Miller, director of research at Radnor Capital Management, a money management firm outside Philadelphia.

Nobody argues about the Tisches' ability to make money.

Laurence, 67, president and chief executive of CBS since 1986, and his brother Preston "Bob," 64, postmaster general during the Reagan administration, parlayed the purchase of a 300-room New Jersey resort hotel into an empire that includes the Loews hotel chain, CNA Insurance Cos., cigarette-maker Lorillard Inc. and watchmaker Bulova Corp.

Rulon-Miller said his firm is buying bank stocks, too, but ones with stronger financials like Shawmut Corp. in Boston, rather than Bank of Boston Corp. or Baybanks Inc.

"But that's what makes it a horse race," he said.

Other analysts agree that bank stocks are a bargain right now -- but not necessarily the ones picked by the Tisches.

"The way I look at the structure and evolution of the banking markets over the course of the '90s, they may have their reasons, but some of their reasons evade me," said Thaddeus W. Paluszek of Kidder Peabody & Co. "They may ultimately prove to be right," he said, although those banks are not "what I'd choose to invest in."