Sept. 21 (Bloomberg) -- Trading in bullish Perot Systems Corp. options jumped to a seven-year high Sept. 18 before Dell Inc. said today it will buy the company for $3.9 billion.

Call volume climbed to 2,539 contracts, or 242 times the four-week average and the most in one day since 2002, according to data compiled by Bloomberg. Only 10 puts traded that day, the data show. The shares, which rose 0.1 percent to $17.91 on Sept. 18, surged 65 percent to $29.56 today in New York Stock Exchange composite trading.

Call options, which convey the right to buy stock at a specified price by a certain date, often return more to investors speculating on takeover targets. Some of the U.S. Securities and Exchange Commission’s biggest insider-trading cases have focused on purchases of options before acquisitions of companies such as Dow Jones & Co. and TXU Corp.

“The question is whether there was insider trading,” said Tamar Frankel, a professor at Boston University School of Law who has testified to Congress on financial regulation. “It’s enough of a bump to warrant attention, and it’s not costly for regulators to inquire.”

Goldman, Morgan Stanley

SEC spokesman John Heine and Dell spokesman David Frink declined to comment. Perot spokesman Marvin Singleton didn’t return a call for comment.

Goldman Sachs Group Inc. and Baker Botts LLP advised Perot on the transaction, while Morgan Stanley and Vinson & Elkins LLP helped Dell.

The last session’s most-active options were October $20 calls, which gained 22 percent to 55 cents Sept. 18 and jumped 1,627 percent to $9.50 today. Those contracts, which expire Oct. 16, are also the most widely owned options, accounting for about half of all 10,353 Perot contracts.

“When there’s a volume spike on a legitimate takeover it smacks of insider trading,” said Steve Sosnick, equity risk manager at Timber Hill LLC, the market-making unit of Greenwich, Connecticut-based Interactive Brokers Group Inc. “What made people wake up Friday and decide to make big bets in upside calls on Perot? That’s the question that has to be asked, and the most obvious answer is probably that someone got wind of the transaction.”

Almost Double

Sosnick’s firm doesn’t make markets in Perot options.

Last week’s call volume of 8,279 contracts is almost double the number that traded during the previous three months, according to data compiled by Bloomberg. Call volume rose to 15,364 contracts today, 28 times the four-week average.

Other factors may explain the trading, such as investments triggered by changes in the price of Perot’s stock, Frankel said.

Dell said in a statement today that it agreed to buy Perot, founded by former U.S. presidential candidate H. Ross Perot, undertaking its biggest purchase ever to compete with Armonk, New York-based International Business Machines Corp. and Palo Alto, California-based Hewlett-Packard Co. in computer services.

‘Worth the SEC’s Time’

Dell, the second-biggest maker of personal computers, offered $30 a share in cash, about 68 percent more than Plano, Texas-based Perot’s closing price on Sept. 18. The acquisition probably will boost profit in fiscal 2012, Round Rock, Texas- based Dell said in a statement today.

“It wasn’t just a random event that they happened to show up the week before a takeover and put on the largest options position in seven years,” said Danon Robinson, the risk manager at Toro Trading LLC, a New York-based options broker. “It’s certainly worth the SEC’s time to make a few phone calls, find out who the customer was and do some investigating.”

To contact the reporters on this story: Jeff Kearns in New York at jkearns3@bloomberg.net; David Scheer in New York at dscheer@bloomberg.net

Last Updated: September 21, 2009 18:13 EDT