* Apple boosts all three major indexes
* ADP payrolls data better than expected in March
* Indexes up: Dow 0.82 pct, S&P 0.79 pct, Nasdaq 0.96 pct (Adds details, changes comment, updates prices)
By Yashaswini Swamynathan and Abhiram Nandakumar
March 30 (Reuters) - The S&P 500 and the Dow rose on Wednesday to their highest this year as investors took comfort from Federal Reserve Chair Janet Yellen's comments that the central bank should tread cautiously on raising rates this year.
Technology stocks led the rally, with Apple's 2 percent rise giving the biggest boost to the three major indexes.
Yellen, in her first remarks since the Fed held steady on rates earlier this month, said inflation in the United States had not yet reached sustainable levels amid uncertainty about China's economy and low oil prices.
Yellen's stance contrasts with recent comments from other policymakers who have voiced support for more than one increase this year.
Markets around the world cheered Yellen's remarks, which suggested that a rate hike was not immediately on the horizon. The dollar fell more than a percent, while bond prices rallied.
Crude oil rose more than 3 percent as reports showed less-than-expected builds in U.S. crude stockpiles last week.
The rally was driven by Yellen's comments but corporate results would be the real test for stocks, said Ernie Cecilia, chief investment officer of Bryn Mawr Trust in Devon, Pennsylvania.
"In order to sustain the strength in the equity market, you're going to have to see some decent earnings growth at some point," he said.
Declining earnings growth has been a major factor for stocks as a sputtering global economy weighs on balance sheets.
Data by payrolls processor ADP on Wednesday showed the U.S. private sector added more jobs than expected in March, suggestive of a continued improvement in the U.S. labor market.
The report is a precursor to the more comprehensive non-farm payrolls data on Friday.
At 10:42 a.m. ET (1442 GMT), the Dow Jones industrial average was up 143.99 points, or 0.82 percent, at 17,777.1, the S&P 500 was up 16.22 points, or 0.79 percent, at 2,071.23 and the Nasdaq Composite was up 46.48 points, or 0.96 percent, at 4,893.11.
Eight of the 10 major S&P sectors were higher, led by a 1.17 percent rise in the technology sector.
Apple was up 2.1 percent at $109.96 after Cowen raised its rating on the stock to "outperform".
Advancing issues outnumbered decliners on the NYSE by 2,170 to 711. On the Nasdaq, 1,891 issues rose and 691 fell.
The S&P 500 index showed 44 new 52-week highs and no new lows, while the Nasdaq recorded 59 new highs and 10 new lows. (Reporting by Yashaswini Swamynathan and Abhiram Nandakumar; Editing by Saumyadeb Chakrabarty)