Record numbers of corporate executives and directors have bought stock in their own companies since the market collapsed Oct. 19, indicating to analysts that those insiders are confident in the future of their businesses.

In the first 30 days after Black Monday, corporate buyers outnumbered sellers 7 to 1. The trend is the opposite of the usual buying and selling pattern of corporate officers and directors, known as insiders. Usually, insider sellers outnumber buyers 2 1/2 to 1.

"I just can't believe what's going on," said Edwin A. Buck, editor of Vickers Weekly Insider Reporter in Brookside, N.J. "If you had bet me that there would be even four insiders buying for every one selling, I would have said you were out of your cotton-picking mind."

Buck said the trend marked the most sustained level of insider buying since he began analyzing insider transactions in 1971.

"Historically, the insiders have never been wrong on the buy side," Buck said, adding that the buying wave indicates the corporate officers believe their stock has bottomed out.

The insider transactions, which must be reported monthly to the Securities and Exchange Commission, are legal as long as they are not based on information that is unavailable to the public.

Some of the insiders bought about the same time that their companies announced programs to buy back stock, a tactic that frequently pushes up the stock price. But there have been no accusations of wrongdoing.

Paul Simmonds, head of research for the Institute for Econometric Research in Fort Lauderdale, Fla., found the same trend as Buck in monitoring insider transactions.

"There has been a spectacular amount of insider buying since the crash," Simmonds said. "The flurry was strongest in the 10 days immediately after the crash, when stock prices were very low, but the trend has continued since then."

Data compiled by Simmonds showed that in the 30 days since the collapse, there were 421 insider buyers compared to 73 sellers on the New York Stock Exchange, 176 buyers compared to 10 sellers on the American Stock Exchange and 643 buyers compared to 83 sellers in over-the-counter trading.

When insiders buy, it is generally viewed as a long-term endorsement of the company's prospects because federal securities law requires them to hold stock for a minimum of six months before selling or return any profit to their company.

"These insiders are not traders," Buck said. "They are looking for the long term. The crash came and they looked at the price of their company's stock and said, 'That's good enough value for me.' "

One substantial buyer has been Kenneth J. Thygerson, president of Imperial Corp. of America, parent company of Imperial Savings Association of California in San Diego, according to data compiled for The Los Angeles Times by the Institute for Econometric Research.

Between Oct. 7 and Oct. 21, Thygerson bought 2,500 shares at prices between $9.125 and $14.25, bringing his total shares in the company to 20,138.

"I'm motivated by the same thing that motivates any other individual investor: Buying something that has good value and should appreciate," said Thygerson, who added that he continued his buying in November. "It is also an indication of some level of optimism about the future of the company."