In the summer of 1999, Dick Cheney, who is now the Republican vice-presidential nominee, repeatedly received the closest thing to a guaranteed profit that the stock market has known: the opportunity to buy shares of technology companies at the initial price that they were offered to the public.

By buying and quickly reselling the stocks of nine companies that were selling shares to the public for the first time, Mr. Cheney made $45,992, an 80 percent return on his investments, according to the statement sent to him by Hambrecht & Quist, a San Francisco brokerage firm. In six of the nine companies, he held his shares for less than a day.

In addition to the nine initial public offerings, as first-time sales are known, Mr. Cheney made three other stock sales last year, all in companies not issuing I.P.O.'s. On those trades, he lost $609, or 1 percent, of his money.

Mr. Cheney's trades were reported on his 1999 income tax return, which he released in nearly complete form at the request of The New York Times. Mr. Cheney's office did not respond last night to requests for comment about the returns.

Representatives of Hambrecht & Quist and the Chase Manhattan Corporation, which agreed to buy the brokerage firm last September, declined to comment on either Mr. Cheney's account or their policies about letting individuals trade I.P.O.'s. Mr. Cheney has a much larger brokerage account at Morgan Stanley Dean Witter, on whose board he used to serve, but he did not report any trades in that account on his and his wife's tax return.

Mr. Cheney's trades are unusual for two reasons, brokers and securities law experts said.

First, he participated in nine I.P.O.'s when more than one would be unusual for an outsider who is not a brokerage client generating significant commissions. Second, he continued to receive access to deals even though in each of the first six offerings he sold his shares the day he bought them. That practice is discouraged by brokers because they want to limit the shares available so that the stock price will rise.

On the three other I.P.O.'s, Mr. Cheney held the stock for periods of five to 29 days.

A founder of the company where the trades were made, Bill Hambrecht, said yesterday that "to get that kind of preferential allocation, you have to be doing something for the underwriter," as the securities firm handling the initial stock sale is known. "When an underwriter is giving away allocations of stock, he knows he's giving away guaranteed profit," added Mr. Hambrecht, who left Hambrecht & Quist before Mr. Cheney's trading began. He now runs W. R. Hambrecht & Company, a firm that is trying to change the way that I.P.O.'s are sold.

While making the trades, Mr. Cheney was chief executive of Halliburton, the oil services company. Guy Marcus, a Halliburton spokesman, said he did not believe Halliburton has ever had a business relationship with Hambrecht & Quist.

Mr. Cheney's trading at Hambrecht & Quist began on July 29, 1999, when he participated in the initial public offering of Net2Phone, a company whose technology enables toll-free phone calls over the Internet.

James Courter, a former Republican Congressman from New Jersey who is the chairman of Net2Phone's corporate parent, the IDT Corporation, said yesterday that he gave the allocation of 1,000 shares to Mr. Cheney as a favor to the former Defense secretary, whom he regarded as a friend.

Mr. Cheney paid $15,000 for his Net2Phone shares and sold them the same day for $26,574, a gain of $11,574 or 77.2 percent.

Several lawmakers received I.P.O. shares of Net2Phone, whose executives have lobbied in Washington against the regulation and taxation of Internet communications. Senator Robert G. Torricelli, a Democrat from New Jersey, obtained at least 1,000 shares at its offering price and resold some of them for a profit,according to his 1999 financial disclosure forms. Representative James H.Saxton, a New Jersey Republican, reported he made between $16,000 and $65,000last year by trading Net2Phone shares.

In a nine-day period in the middle of August, Mr. Cheney was allocated shares in four more initial public offerings, all of which he sold at a profit on the day he bought them. He participated in two more I.P.O.'s in September, one more in October and one in November.

Mr. Cheney's press secretary, Juliana Glover Weiss, did not respond yesterday when asked how much money Mr. Cheney had deposited in the Hambrecht & Quist account or if it was still open. The trading records indicate Mr. Cheney deposited as little as $15,000.

Mr. Cheney and his wife, Lynne, had previously disclosed only the first two pages of their tax returns for 1990 through 1999, holding back the supporting documentation that show details of investment income.

No law requires officials or candidates to make their tax returns public, but Mr. Bush has provided The New York Times with copies of his complete returns since 1994. Vice President Al Gore has disclosed his complete return each year since 1991 and Senator Joseph I. Lieberman, after he was nominated by the Democrats for vice president in August, released his complete tax returns back to 1990.