Oils also finished on the down side, after enjoying advances last Thursday and Friday related to options expirations.

A round of computer-assisted "buy" orders related to today's double-witching options expiration was a factor in the stock rally.

Thus, the options expirations can sometimes lead to a frenzied burst of buying or selling stocks, as they did yesterday.

He did see portfolio adjustments in advance of this Friday's options expiration.

Could the cause of this clustering have nothing to do with options expiration?

Trading showed little of the volatility that had been feared for the first test of the new procedures for options expirations.

"Coupled with options expirations, the market managed to maintain its tone."

Once the options expiration plays out, you could see a lot of downside action.

Between options expiration and dealers repositioning themselves for next week, market volume was higher than an average summer Friday, according to Govpx, a bond pricing service.