The Federal Reserve will make its regular monetary policy announcement on Wednesday and without question, Wall Street will be watching.
To one stock market observer, though, the second-quarter gross domestic product figures also due on Wednesday is "the biggest wildcard this week" and more likely to move markets.
After all, GDP has been very tough to gauge lately.
"Coming in at -2.9 percent last quarter was a shock to everybody," David Zervos, chief market strategist at Jefferies, told CNBC on Tuesday. "I think, you know, that [the GDP number this week] could be very high or very low and really get some people sort of hot and bothered."
GDP is the total value of all goods and services produced within a country over a given time, so it's a gauge on the health of a country's economy.