The SEC is studying further program trading rules.

Some of the moves being considered include limiting the numbers of index options that an investor may hold at any one time or increasing margin requirements, which is the amount of money that must be put up to buy a contract, according to Richard Ketchum, director of the commission’s market regulation division. The SEC also is studying whether to limit stock index call options, which are similar to short sales in which an investor sells borrowed securities in the hope that the price will fall and they can be bought back at the lower price.