The National Association of Realtors said its Pending Home Sales Index, based on contracts signed in April, rose 6.7 percent in April to 90.3 from 84.6 in March.
It was the biggest monthly increase since October 2001 and it took the index 3.2 percent above its year-ago level in the latest sign the battered U.S. housing sector was stabilizing.
Economists polled by Reuters ahead of the report were expecting pending home sales to rise 0.5 percent.
The downturn in the U.S. housing market touched off a global credit crisis that sent economy's worldwide tumbling into recession. Now, signs are emerging that the global economy is beginning to heal.
The association's senior economist, Lawrence Yun, credited improved home affordability and a new government program that provides an $8,000 tax credit for first-time homebuyers for the surge in buying activity.
The NAR said its Housing Affordability Index, which blends factors like home prices and mortgage rates, was in record territory with 30-year mortgage rates hovering around 5 percent and an abundance of homes on the market.