Amex reopens; other exchanges benefited from its shutdown.(Chicago Tribune)

A wounded American Stock Exchange officially reopened Monday for the first time since disaster struck the nearby World Trade Center three weeks ago.

The shutdown cost Amex traders considerable business _ with the Chicago Board Options Exchange among those gaining market share at the expense of the New York bourse. But even though Amex traders may have trouble regaining what they lost, exchange officials remained grateful for help they received within the industry.

"We got a place for our customers to send their orders and for our members to trade under very difficult circumstances," said Michael Bickford, senior vice president of the American exchange's options group.

The New York Stock Exchange listed Amex equity products, and the Philadelphia Stock Exchange made room for Amex options products and members.

Still, the market-share shift was dramatic. Although the options market traded 5.8 million fewer contracts in September than August, only the Amex saw a drop in contract volume, according to preliminary figures from the Options Clearing Corp.

Typically the nation's second-largest options mart, Amex traded just 4.6 million contracts in September, giving it 8.7 percent of a market in which it previously garnered 28 percent.

The all-electronic International Securities Exchange in New York gained the most market share in September, building on its already meteoric rise in the industry. Its September share was 12 percent, nearly double its average market share for the year of 6.5 percent.