The data reflects contracts but not closings, which take a couple of months to complete.
Through the first three months of the year, closings were the highest in five years for the quarter.
Yun said this year is expected to be a year of recovery for housing and that the latest contract signing activity suggests the second quarter will be just as good as the first.
February's figures were upwardly revised to 97.4 in February and is 12.8 percent above March 2011, when it was 89.9.
A level of 100 represents a healthy market.
Regionally, the results were mixed.
The index for the Northeast slipped 0.8 percent to 78.2 in March but is 21.1 percent above the March 2011 level. In the Midwest, the index declined 0.9 percent to 93.3, but is 16.9 percent higher than a year ago. Pending home sales in the South rose 5.9 percent to 114.1 and are 10.6 percent above last year's level. The West saw an 8.7 percent increase to 108, 9 percent higher than a year ago.