The Dow Jones industrial average jumped more than 200 points, joining a surge in global markets, after European leaders agreed to easier bank bailouts and regional oversight for their troubled financial sector.
Leaders in Brussels unveiled a plan to funnel money to banks directly from a regional bailout fund. They also agreed to ease austerity measures that are causing political unrest and agonizing recessions in Greece and other nations that have received bailouts.
Fear about Europe has weighed on markets in recent weeks. Signs of improvement there tend to spark broad, if temporary, rallies, said Uri Landesman, president of Platinum Partners LLC, a New York hedge fund. Landesman expects plenty of sharp leaps and dives this summer as traders continue to speculate about Europe's future.
"This Europe thing is going to trade up and down based on the news of the day," Landesman said.
The Dow Jones industrial average rose 214 points to 12,815 as of noon EDT. The Standard & Poor's 500 index rose 25 to 1,354. The gains were broad, with losses for fewer than 20 of the 500 stocks in the S&P index.
The Nasdaq composite average gained 66 points to 2,915.
The S&P 500 has risen 3.4 percent this month, and is on track to end its strongest June since 1999. But because of a deep slump in May, as Spain's banks teetered near collapse, the market is headed for its worst quarterly loss since last fall.
There may be more damage in store, Landesman said. "I remain quite negative about the market in the next two months," he said, adding that lower trading volumes during the summer can lead to choppier trading.
The other big challenge was a broad slowdown in the global economic engines of Asia and the U.S. China's expansion appears to be cooling, and U.S. employers have created very few jobs in the past three months. The June U.S. jobs report, due out next Friday, is expected to show a fourth straight month of anemic job growth.
Yet on Friday, traders in nearly every corner of the market appeared jubilant. They sold U.S. Treasurys, sending the yield on the 10-year Treasury note up to 1.64 percent from 1.57 percent late Thursday, as demand decreased for ultra-safe investments.
Energy prices rose, on the theory that a cure to Europe's debt woes will remove one of the major drags on global growth. Benchmark oil jumped 5.5 percent, or $4.30, to $81.98 a barrel on the New York Mercantile Exchange, a day after hitting an eight-month low.
Industrial and information technology stocks rose the most of the 10 industry groups in the S&P 500. Those companies would benefit from faster growth and stronger demand from Europe, a key trading partner.
The euro gained 2 percent against the dollar, rising 2.5 cents to $1.2685. As the dollar fell, gold gained more than 3 percent, rising $47 to $1,598 an ounce. Gold and the dollar tend to move in opposite directions because they compete for cash that traders want to park in ultra-safe investments.
The two-day summit in Brussels is the 19th meeting for European leaders since the debt crisis emerged, and leaders have repeatedly clashed over how best to address it. European Council President Herman Van Rompuy called Friday's agreement a "breakthrough."
Consensus in Europe was reached after borrowing rates in Spain — where unemployment is approaching 25 percent — and Italy hit unsustainable levels. The fear was that the weaker economies of Europe would drag the entire continent into recession, or worse.
Stocks around the world surged Friday, with markets in countries on the front line of the crisis doing particularly well. Italy's FTSE MIB closed up 6.6 percent, Spain's IBEX 5.7 percent.
The yield on Spain's 10-year bond dropped by 0.56 percentage points to 6.34 percent as demand for the bonds increased. Italy's benchmark bond yield fell 0.28 percentage points to 5.79 percent. The lower yields reflect greater confidence among investors that the countries will be able to repay their debts.
In corporate news, Blackberry maker Research in Motion plunged 19 percent after the company, based in Canada, posted quarterly results that suggest it is crumbling faster than thought. RIM is cutting 5,000 jobs and unexpectedly delaying the launch of new phones deemed critical to its survival.
The biggest gainer in the S&P was the alcoholic beverage giant Constellation Brands. The stock jumped 23 percent after the company secured the right to distribute Corona beer and other popular brands in the U.S. Constellation bought the other half of Crown Imports LLC from Grupo Modelo for $1.85 billion.
Nike plunged 8 percent, the biggest drop in the S&P 500. The world's largest athletic shoe and clothing company said profit dropped 8 percent last quarter on high product costs, a restructuring charge and an unexpected customs assessment.