The Chicago Board Options Exchange delayed its opening on Thursday and there has been no trading so far in the morning.
The reason could not be immediately determined, but it appeared to be a systems outage.
A CBOE spokeswoman said that she had no information on when CBOE would open. The delayed open means investors cannot trade CBOE's exclusive options on the S&P 500 Index and the CBOE volatility index. CBOE is run by CBOE Holdings Inc.
Trading continued on the other U.S. options exchanges.
"There appears to be no trading at all from the CBOE," said WhatsTrading.com options strategist Frederic Ruffy.