As traders await the 3:25 PM ET full reopening of the Nasdaq, the anticipation is that the picture isn't going to be pretty.
A problem that began at the Nasdaq spread through the trading world and has market pros on edge for what is next.
"I've never seen anything like this in my life," said Dave Rovelli, managing director of U.S. equity trading at Canaccord Genuity. "It's horrible."
Once trading gets the OK to start again, traders will get a five-minute grace period in which they can submit quotes, trade imbalances and conduct other business matters.
Dozens of publicly traded companies, including high-profile companies such as Apple, Microsoft and Facebook, were showing their shares halted. The Nasdaq status message was time stamped at 12:14:03 ET.
When it re-opens, things could get interesting.
A spike in volume will be likely, particularly from computerized trading programs that aren't set up to handle a lengthy shutdown from a major global exchange.
"You will have some pent-up activity," said Dave Lutz, managing director of trading at Stifel Nicolaus. "Algos are going to try to make up for an hour and a half you missed, which could seriously skew an illiquid security."
The effects will not be universal.
At some desks, Lutz said, the problems at the Nasdaq were barely noticed.
"We're calling all our customers. They're updated with what the Nasdaq is intending to do," he said. "You have to make sure your customers are not caught with their pants down once they start trading again."