Wall Street ends flat as recent rally spurs caution

"I think people are starting to become concerned about valuation here," said Stephen Massocca, chief investment officer at Wedbush Equity Management in San Francisco. The Dow Jones industrial average closed up 21.57 points, or 0.12 percent, to 17,623.87, the S&P 500 gained 2.02 points, or 0.1 percent, to 2,051.6 and the Nasdaq Composite had added 13.23 points, or 0.28 percent, to 4,808.87.