Group One Trading is one of the leading proprietary option trading firms in the United States. The company staffs more than 100 employees, and over 50 agents trading in over 1,900 listed equity and equity index options. Group One Trading is one of the leading firms on five exchanges, including the American Stock Exchange, Philadelphia Stock Exchange, Chicago Board Options Exchange, Pacific Exchange, and the International Securities Exchange. The company owns specialist posts on the exchanges. Group One is developing several projects to complement its equity options floor market-making operations. In addition, it is a growing electronic trading team making markets in the International Securities Exchange. Group One Trading is located in San Francisco.