The average 30-year fixed mortgage interest rate fell from 3.41 percent to 3.39 percent with an average 0.7 points, Freddie Mac said.
A year earlier, interest rates for 30-year, fixed-rate loans were at 4 percent.
For 15-year loans, interest rates fell from 2.72 percent to 2.7 percent with an average 0.7 points. A year ago, 15-year loan rates averaged 3.31 percent.
Average interest rates for five-year adjustable-rate mortgages were down from 2.75 percent to 2.74 percent with 0.6 point. In the same week of 2011, rates for five-year ARM contracts stood at 2.96 percent.
The average interest rate for one-year ARM contracts fell from 2.59 percent to 2.58 in the week with 0.4 points.
Rates a year ago for one-year ARM contracts averaged 2.88 percent.
Low inflation and a growing economy allowed interest rates to fall slightly in the week, said Freddie Mac vice president and Chief Economist Frank Nothaft in a statement.