Last month the Standard & Poor's 500 index logged its first monthly decline since October after Federal Reserve Chairman Ben Bernanke said the central bank could ease back on its stimulus this year if the economy continues to recover.
The Dow Jones industrial average was up 146 points, or 1 per cent, at 15,054 at midday Monday.
The S&P 500 was up 17 points, or 1.1 per cent, at 1,623. The S&P 500 had its best first half of a year since 1998, returning 13.8 per cent with dividends reinvested.
The Nasdaq composite was up 44 points, or 1.3 per cent, at 3,447.