The Leading Economic Index has now gained in seven of the past eight months. In May it rose to 95.8, following a drop of 0.1 percent in April.
Economists had predicted a 0.1 percent gain.
The Leading Economic Index, which takes into account 10 economic components, is essentially a comparison with 2004, the year the Conference Board assigned a level of 100.
Despite the increase, "Weakness in the average workweek in manufacturing, stock prices and consumer expectations kept the Leading Economic Index from rising further," said Conference Board economist Ataman Ozyildirim.