Chesapeake Energy did not disclose the size of the stock sale, pending the filing of documents with the Securities and Exchange Commission, but media reports have placed the number of shares at more than 33 million, making him the Oklahoma City-based company's third largest shareholder.
"I am very disappointed to have been required to sell substantially all of my shares of Chesapeake," McClendon said in a news release. "These involuntary and unexpected sales were precipitated by the extraordinary circumstances of the worldwide financial crisis."
"I have been the company's largest individual shareholder for the past three years and frequently purchased additional shares of stock on margin as an expression of my complete confidence in the value of the company's strategy and assets."
Last month, Forbes showed McClendon at No. 134 on its list of the nation's 400 richest people, with a net worth of $3 billion, an increase from $2.1 billion the previous year.
A margin loan is a loan made by a brokerage house to a client that allows the customer to buy stocks on credit using securities. When a stock dips below a certain point, brokers who lent investors money through margin agreements demand that the investors sell part of the stock or pony up cash to cover losses.
McClendon said he looked forward to rebuilding his ownership position in the company. He and Tom Ward co-founded Chesapeake Energy, the county's largest producer of natural gas, in 1989.
Both men are members of an ownership group that recently purchased the NBA's Seattle SuperSonics and the Seattle Storm of the WNBA for $350 million. A group of Seattle businesswomen purchased the Storm from the group, but the Sonics franchise was moved to Oklahoma earlier this year after much legal wrangling and the team was named Oklahoma City Thunder.
Dan Mahoney, a spokesman for Thunder chairman Clay Bennett, said Bennett would have no comment on McClendon's continued involvement in the ownership group.
Chesapeake's stock closed October 10 on the New York Stock Exchange at its lowest price of the year, $16.52, down $1.19, and well off the $74 top of its 52-week range. The price of natural gas also has plunged, due in part to mild autumn weather and abundant supplies heading into the winter heating season. Last month Chesapeake announced it was scaling back its drilling capital expenditures budget through 2010 in response to falling natural gas prices.